People always look at me like I'm crazy when I talk about non-24. If left to my own devices I'll just go to bed an hour later each night, I can get into a bit of a midnight to 2am schedule also, but then pop a later night in order to be tired enough the next night to rest back a few hours.
Also recently diagnosed ADHD (in my 40s), and apparently sleep issues like non-24 are at least correlated to it.
Have you also observed that you're better able to adapt to the 24-hr day when you're not working and getting regular outdoor activity and exercise? I really think working with computers indoors is a large contributing factor to my non-24.
It's hard to say. I was doing a lot of hiking and outdoor activity last summer, and it didn't really make that much difference (if anything, being in better shape gave me more energy at the end of the day).
I do find I have an energy slump in the early evening and wonder if there is some way to take advantage of that, but haven't been able to push myself to try a sleep schedule change that drastic (and my hunch is that it'd just push that slump earlier and I'd start drifting again, just starting from an earlier point in the evening).
Also recently diagnosed ADHD (in my 40s), and apparently sleep issues like non-24 are at least correlated to it.