Edited Study Taken from Amy Van Gerpen
[words in brackets are mine]

Matthew 24:32-33 - "Now learn this lesson from the fig tree: As soon as its twigs get tender and its leaves come out, you know that summer is near. Even so, when you see all these things, you know that it is near, right at the door.

Jesus had finished answering the question about His Coming, when he switched gears here and began to answer the questions about the signs of the end of the age. The first sign that showed that the end of the age had arrived was the fig tree shooting forth its leaves. The fig tree is one of the last trees to bud in the spring. So when it puts forth leaves, people know that summer is right around the corner. What does the fig tree represent?  Israel (Hosea 9:10; Isaiah 5:7; Ezekiel 36:8-12; Amos 9:14-15).

…the fig tree would represent the nation of Israel, based on Jesus' prophetic parable that pointed to the 70AD destruction in Matthew 21 and the rebirth of Israel in Ezekiel 36 and Amos 9. The vine would represent the spiritual state of Israel based on Isaiah 5. The olive tree would be associated with Israel's salvation based on Romans 11.

The "Trees" of Israel (Judges 9)
Israel as the Nation = The Fig Tree (Matthew 21)
Israel's Spiritual State = The Vine (Isaiah 5)
Israel's Salvation = The Olive Tree (Romans 11) 
“Even so, when you see these things happening, you know that the kingdom of God is near.– Luke 21:31

Notice in Luke 21:31 above that the "kingdom" is near when "all the trees" are budding. The use of "kingdom" with "all the trees" may be indicating that the vine (spiritual) and olive tree (salvation) of Israel will start to bud shortly before the Millennial Kingdom begins, which was foretold to occur in Ezekiel 37 and Romans 11.

Ezekiel 37:13-14 Then you shall know that I am the LORD, when I have opened your graves, O My people, and brought you up from your graves. I will put My Spirit in you, and you shall live, and I will place you in your own land. Then you shall know that I, the LORD, have spoken it and performed it," says the LORD.
Ezekiel 37:24-28 David My servant shall be king over them, and they shall all have one shepherd; they shall also walk in My judgments and observe My statutes, and do them. Then they shall dwell in the land that I have given to Jacob My servant, where your fathers dwelt; and they shall dwell there, they, their children, and their children's children, forever; and My servant David shall be their prince forever. Moreover I will make a covenant of peace with them, and it shall be an everlasting covenant with them; I will establish them and multiply them, and I will set My sanctuary in their midst forevermore. My tabernacle also shall be with them; indeed I will be their God, and they shall be My people. 28 The nations also will know that I, the LORD, sanctify Israel, when My sanctuary is in their midst forevermore.
Romans 11:25-26 For I do not desire, brethren, that you should be ignorant of this mystery, lest you should be wise in your own opinion, that blindness in part has happened to Israel until the fullness of the Gentiles has come in. And so all Israel will be saved...
The book of Habakkuk is about the judgment of Israel by the Babylonians. For the trees not to bloom and bear fruit here shows how the nation of Israel fell; both physically and spiritually. Therefore, the blooming and bearing of fruit of the trees would show the restoration of Israel. Notice that the same trees listed here are those in the the parable of the trees in Judges 9.

It appears that the sign of the fig tree is the beginning of the last generation before Jesus returns. How long is a generation? How does the Bible define a generation? What is the context and starting point of a generation in this passage? The Bible tells us the following:

120 YEARS - TIME UNTIL JUDGEMENT DURING THE DAYS OF NOAH. - God allowed 120 years for Noah's generation to repent before the flood. (Genesis 6:3)

100 YEARS - PROMISE OF RETURN TO THE LAND - Egypt was in captivity for 400 years or 4 generations of 100 years each - Also, there have been 4 different generations of God's chosen people that have been promised a return to the land (Abraham, Exodus from Egypt, release from Babylon, the Balfour Declaration). (Genesis 15:13-16)

70-80 YEARS -NATURAL LIFESPAN OF MAN - Psalm 90:10 gives us a range of 70-80 for the average lifespan of man. [This is the last Scripture we seem to have concerning what a generation might be defined as.]
Psalms 90:10 The days of our lives are seventy years; And if by reason of strength they are eighty years, Yet their boast is only labor and sorrow; For it is soon cut off, and we fly away.
What are "all these things"? Jesus had been describing "all these things" throughout the discourse; they are all the things that will occur before He returns. Now He is answering the question about the end of the age, so the fig tree budding would be the starting point of "all these things". It appears that the context here, then, is about the life of that generation to see Israel becoming a nation again.

If this is true, the life of the generation would be 70-80 years. The signs rapidly converging around us show that this length is reasonable. It is also interesting to note that all the prophecies regarding the Jewish exile and the destruction of Jerusalem and the Temple in Luke 21 all occurred within the normal lifespan of 70-80 years from the birth of Christ.

A word of caution here: Though, the 70-80 year generation argument is convincing, we need to be careful of pinpointing dates. We know that the Word of God was inspired and designed with purposeful patterns and symmetry and it would make sense if the Scriptures point to the time of the 2nd Coming. However, we don't have the luxury of having the exact number of years set out for us like they did in Daniel 9:24-26 for the first time Christ came to Earth.

We are only human, so it is probable that our interpretations are not all correct. Therefore it is prudent to not get hung up on dates, because at this point it is an educated guess. The point of all this, even without dates, is that we know just from the signs that time is rapidly running out. Besides, we never know when our time on Earth is up. Therefore, it is best to busy ourselves to further the Kingdom and be ready to meet Jesus today.

[In addition]
Luke 13:5-9 contains the first parable of the fig tree.

“I tell you, no! But unless you repent, you too will all perish."  Then he told this parable: "A man had a fig tree, planted in his vineyard, and he went to look for fruit on it, but did not find any.  So he said to the man who took care of the vineyard, 'For three years now I've been coming to look for fruit on this fig tree and haven't found any. Cut it down! Why should it use up the soil?' " 'Sir,' the man replied, 'leave it alone for one more year, and I'll dig around it and fertilize it. 9 If it bears fruit next year, fine! If not, then cut it down.' "

In Isaiah 5:7 we see that the vineyard belongs to the Lord. The keeper in Luke 13:5-9 is Jesus, who was three years into His ministry at the time. Right before the parable in Luke 13:5, Jesus warned that unless Israel repented, the nation would perish. In the parable, God told Jesus to cut down the tree, which is Israel. Jesus asked to give the tree another chance until the next season before cutting it down.
Jesus was to spend the next half year trying to bring fruit out of the nation of Israel before giving up on them. The cursing of the fig tree later in Matthew 21 shows us the verdict of the nation Israel. Though Israel as a nation would be destroyed, individual faith and salvation would still be available, as we see at the end of the following passage:

Matthew 21:18-22 Now in the morning, as He returned to the city, He was hungry. And seeing a fig tree by the road, He came to it and found nothing on it but leaves, and said to it, "Let no fruit grow on you ever again." Immediately the fig tree withered away. And when the disciples saw it, they marveled, saying, "How did the fig tree wither away so soon?" So Jesus answered and said to them, "Assuredly, I say to you, if you have faith and do not doubt, you will not only do what was done to the fig tree, but also if you say to this mountain, 'Be removed and be cast into the sea,' it will be done. And whatever things you ask in prayer, believing, you will receive."

[The nation of Israel has been "planted" since 1948.  The nation has also been "budding" in different ways as well, but seems to be showing more of this process in frequency and grand display/intensity lately.  What many biblical, end-time scholars call the Tribulation Period is a time for the recalling and refining of Israel (Daniel 9:24).  The more signs we see setting the world up for that Period the closer believers in Christ are to the Rapture.  This is why I share this information with you, as a fellow believer in Christ, SO THAT, we might keep one eye on Israel, the other on the sky - all the while telling others (non-believers) about Jesus' soon return and His love for them.]