I have to agree with the other poster on this. I only full compile once in the beginning and once at the end. Every other time, I just recompile the changed part and rebuild it with the unchanged object files.

But if you're talking about packages from source, then I agree. It's the one thing that sometimes makes me question whether or not I should upgrade. But, after a full night of compiling Qt5 from source, that lingering doubt usually vanishes.