I'm not sure I want to go back to a world where I could lose a few hours work because I didn't save my work incrementally. (That said, as others suggest, you want to have a way to say known good/useful checkpoints as well.)
If you used programs like Lotus back in the day, you'd realize that that you tended to develop muscle memory to just quit in many cases. You also had crashes that kept you from saving as well.