I tend to think of it the length of time that the child is awake. So at the moment my dd has just lengthened her activity time from 2.5hrs (she's 9mths), she was taking 30mins to get her to go to sleep after previously falling asleep within 5mins of being put in her cot. So to me that meant that she was capable of having the extra 30mins added to her activity time. So, yes (after all that long-winded explanation :wink: ) I think that you're over the 1.5hr mark if it's taking that long for him to go to sleep. Of course if you think he's getting overstimulated and overtired by that time it's not the optimal time to be awake. It sounds like maybe he likes that time to himself to winddown on his own and that's great, nothing wrong with that. I would keep him up with you though for as long as possible so you don't end up with him being in his cot for too much activity time by himself.