This is exactly how I feel. That 1.5 - 2 hours each night when I know no one wants or needs me to do anything is invaluable for me mental health. I know I should get more sleep but I need that time to not resent the fact that I get so little time for "me". I get to work at 4:30am (time zone thing) and do a lot of the primary child care and chores. It's often 8:30pm before I'm done and even then the dogs water bugging me to go out, etc. My wife needs sleep so she heads up early and I just putter or stretch, sometimes I write a little code, or watch part of a show. Feels good.