I know the feeling. In college (and for a year or so right after), I had the same answer.

A few years later, I've finally realized that any code I write at 2am almost always needs to be fixed--often substantially--soon after. I miss things. I write stupid bugs. I don't see the requirements clearly.

I've found writing things down (sometimes a few words, sometimes a few pages), sleeping on it, and reviewing those notes first thing in the morning--before email, before showering, before anything--to be a much a better strategy.

YMMV, of course.

After you create your masterpiece of code, do you know enough to document and understand it later (so you can pass it on to others)?

Having been in the zone, I completely sympathize with the view that productivity isn't constant; that the cost to your health is worth the leap...

Have you ever had that feeling and then realized in the morning/next day that your feeling was illusory and you actually took the harder path?

For me it's more about getting the idea out of my head. The code wouldn't be a finished product, but more like a brain dump.