My 2 1/2 yr old DD gets up at 8/8:30 almost like clockwork, so we use that to determine her bedtime. She seems inclined to be night owl like her daddy, so I can't push up her bedtime too far or she pops up and wants to go hang with him. I feel good if she's asleep by 10pm, in bed by 9:30.
She takes up to a 2 hour nap in the day, starting anywhere from 2pm to 4pm. When she was younger I tried to get her on a more "socially compatible" sleep schedule, pushing it earlier, but this is where she gravitates back to. It's ok with me! I like the hour to myself in the mornings, though DH and I do miss our evenings.