In my experience, the opposite is often the case -- The argument: "We can't start over because we don't have enough time left" grows in strength as the project approaches the deadline and is used to justify shoddy work. (You paint yourself into a corner.)

I guess one aspect why "agile" stuff is effective, is that the "last day" (on which it becomes surprisingly easy to make all the decisions that couldn't be made until now) happens multiple times and earlier in the project.