I had a very similar experience. My wife hits the sack at 11-ish, and I'm up until 3 or 4 working on side projects. It has worked out very well for us.

I asked her to read "Hackers and Painters" while we were dating. She did and said that it made her understand why I am the way I am. So, if you're early in a relationship and want her/him to "get it"... I highly recommend the book.

I got to personally thank PG for it a couple years ago... but... thanks again!