> Why does the size of the work that needs to get done matter? If you need it you need it.

Generally, I would agree, but I've seen cases where it mattered, because the value of a feature would become 0 after a set date. For instance, we needed a specific feature to fulfill the requirements for a (massive) contract, and you could only apply for the contract until a specific date. The value of this feature outside this scope was pretty much zero.