I think an hour to 1.5hrs is the awake time for this age group. I was a bit if a clock watcher to start with as I just couldn't pick tired signs. DD would yawn within 10 mins of being awake so that wasn't a sign for us. So I would just try and gether back to sleep within an hour or so of waking up. If it went past 2 hrs and she wasn't alseep I would then push/bounce/rock/carry her to sleep. If she became overtired she became v cranky and v hard to settle. Even now I make an effort to keep DD awake for a certain amount of time during the day or else she will just sleep and sleep all day and be awake all night.