There’s a wonderful Millay poem on sleep that was, at one time, written on a stairwell at my school:
My candle burns at both ends;
it will not last the night.
But ah, my foes, and oh, my friends —
it gives a lovely light!
– Edna St. Vincent Millay
It’s a beautiful image, but don’t let its beauty fool you. Staying up late is not a virtue — it’s a form of greed.
Don’t steal from tomorrow! Don’t be so arrogant as to think you will run out of time before you run out of ideas. Be responsible, not arrogant… but of course, allow yourself the occasional late night when circumstance (or your spirit) so demands.