There are such things as "big days". If you have a degree to finish, a conference paper, a demo, a seasonal feature, a lucrative work project, etc. Those are the times when I might neglect my body for 1-2 weeks, sometimes up to 4. Sure, you do have to return back to a normal, stable life after that and maybe have a little break.

In all aspects of life, success is about performing at your peak at just the right time.