DD (4yrs, 3 mths) is almost at the stage where she is ready to sleep on the top bunk (we planned ahead and bought bunks two years ago in anticipation of two children lol). She's been practicing climbing up and down for a few months now and is very keen to sleep up there (although she has no need to sleep up there for at least another 18 months!) but my biggest concern is how she will go climbing down half asleep. She takes after me and is slightly unco, and while she does fine going up and down during the day, I'm quite sure she'll fall flat on her face right now if she was to sleep up there and try to climb down half asleep. I'll probably delay her for at least another few months. I think they're ready when they are able to climb up and down without issue.