What is the lifetime of the fund? Just the amount of time that the VC firm has said they would have all the money (and more!) back to the limiteds? Clearly that's not a hard deadline, right?
It is a hard deadline because it is in the deal documents when the fund is formed. It is relevant because the fund management is guaranteed fees for that period. Extending it is usually straightforward, but the compensation of the fund management team during the extension is open for negotiation.