I always had pretty severe DSPS for most of my adult life. Luckily I usually had the flexibility to accommodate a super night owl schedule.

What "cured" me was having kids. I now have no problem falling asleep at 10 PM. I would guess it's due to pretty brutal sleep deprivation (our first took a very long time to get through the night). I'm guessing this pretty much smashed my pre-existing circadian rhythm.