Three Year Old SleepAt the age of three our girls needed roughly twelve hours of sleep. Our second DD probably needed a little more than our first DD, but they were pretty comparable in terms of the amount of sleep that they needed.
Kids are different though, and you can't necessarily tweak sleep. In fact, I think you're quite lucky if you can do it. A lot of preschoolers are really hard wired, especially for wake-up times.
Our oldest would always sleep for exactly twelve hours at night. If something kept her up late, she slept in late the next morning. In contrast, our younger DD always woke up at the same time, and we had no choice but to work backwards from that.
Our girls are 5 and 6 now. They are still somewhat like this, but it isn't as pronounced now that they are older. Younger DD can sleep in a little bit now, though not as much as she needs to when she's up late, and so it's still important to watch when she gets to bed. Older DD is still inclined to sleep in if she needs it, but not quite as much as she used to.