I wouldn't have thought that it would be too late for a gate as such, but I know that both of mine much prefer hanging on to me than playing by themselves! dd1 never had particularly free reign - we pretty much stayed in one room when she was playing - but dd2 has always been able to meander around downstairs, and they have both turned out to be pretty rubbish at playing independently. I would say that dd2 is better at it than dd1, so I think it is much more to do with character than habit iyswim.