The short summary is that I "cured" my N24 (Non-24-Hour Sleep-Wake Disorder) using modest doses of melatonin, with occasional light therapy. I would take 0.25 mg of melatonin at 6 pm, and usually another 0.25 mg at 11 pm. I fell asleep around midnight. I even got to the point where I was only taking melatonin about twice per week, and only using light therapy about 2-3 mornings per week.
HOWEVER, this also made me so sick (specifically, fatigue) that I was completely unable to function for more than an hour or two each day. I saw several specialists and was treated or tested for everything from sinus infections to Lyme disease to cystic fibrosis. My primary care physician literally gave up. He said that he had another patient with similar symptoms who just "got better" after a year, and maybe the same thing would happen to me. I got to the point where I started thinking that I had some terminal disease (like cancer) that was draining all my energy. Or some weird form of depression that was manifesting itself as fatigue without any of the traditional symptoms (like hopelessness, weight change, etc.)
Then one day I looked at my sleep log and my health log and realized that my health had gone downhill at the same time that I "cured" my N24. So, after 5 months of living like a lark for the first time in my life, I stopped all the melatonin and light therapy and went back to sleeping when my body wanted to (on a 24.75 hour day). And within a week I felt about 90% better.
You would think that after a few years on a sleep disorder email list, I would be smart enough to realize that forcing myself onto a 24-hour day might be the cause of my severe fatigue. But I was so glad to finally have cured my N24 with the right treatment. And I LOVED living like a lark. And my fatigue was so strong and so foreign (it didn't feel like "sleepiness") that I just didn't make the connection.
As of right now, I haven't taken melatonin for about 4 months.
If I need to be awake when my body wants to sleep, I just force myself out of bed, knowing that I only have to do it for one or two days. If I need to drive, I take 125 mg of Nuvigil and wait an hour for it to kick in. I go right back to my natural sleep schedule as soon as I can.
I had a family event this summer where I just poured myself into the passenger seat, rode for two hours, was a zombie for four hours, and then rode home for two hours. Thankfully my wife was willing to drive. I was so sleepy that I don't remember any of it. In fact, I currently can't even remember what the event was. I think it was a birthday. I think it was at my sister-in-law's house. But I'm not sure.