Before I retired 20 months ago, I typically got up at 6:00 a.m. weekdays and slept in a little on weekends. After retiring, I was "sleeping in" until around 8:00 a.m. or so.
Gradually that time crept forward to 9:00, 9:30, 10:00 ... I guess it's because I know I can stay up as late as I want and I often do. Also, after years of six hours' sleep, and often waking up at 4:00 a.m. worrying about deadlines, it's such a luxury to wake up in the morning and realize I don't have to get out of bed just yet if I'd rather not. I find I'm at my best on about nine hours of sleep.
On average I'd say I get out of bed around 9:30 a.m. these days. When I have to get up much earlier because of an appointment, travel reservations, or whatever, I really feel it.