I have never worked on a huge project, as I am still a student and my programs rarely gets bigger then 5.000 lines. When Im programming I am constantly compiling my program. I do it to make sure that the new code is working correctly, to check that the new code did not break any older code and I find it to be an easy way of finding syntax errors.
But, when reading articles I often hear about compile times much higher then an hour. How do people work then? Do people only compile over night and just hope it is all working when they get back?