I moved Zhai into a big bed when he was 16months coz he didnt seem to have enough room. He kept on kicking the side of his cot in his sleep and headbutting it so we did the switch. He has only fallen out once, but apart from that he has been great! At first i had to stay in there till he went to sleep but i just edged out of the room. And i left the cot up in his room. I have re-made it for bubba and put stuffed toys in it, although Bubba is going in our room in a bassinette for a while. I may put bubba in the cot for day sleeps?? I dont know.
Goodluck.