We did it last week, DD is 18 months old. We did it because she has been having a horrid time sleeping and became a bit anti-cot (would get rigid in my arms even while asleep if she knew she was going in), so we converted the cot to the bed. She's still having a horrid time sleeping, but at least she's sort of willing to get into it now. Cutest thing is that at night she still hasn't worked out she can get out, so sits up and cries for me to go and get her.