Fair enough. But FTR the 12-1a habit was itself a form of restraint against my prior tendency to stay up much later than that -- as a parent of school-aged kids, w/ no plausible option to sleep past 7a or so. Staying up till 3 or 4 and getting less than 4h sleep would've been a non-starter.

Yeah, I feel the pain. I usually go to sleep between 3-5 and need 8-9 hours of sleep. If my work didn't allow for very flexible schedule I fear I'd also need to resort to extreme measures (cold showers - brrr).