P.T.
My son is 2 months shy of age 3 and he is still in the crib. He only climbed out once around 18 months and he scared himself so much he didn't try it again. He has been perfectly happy in it and I loved knowing he was safe and not roaming.
We are now getting him a bed because he is starting to get uncomfortable in the crib - because he is getting bigger. I have read that a child "should" be moved to a bed between the age of 2 and 3.
The moms I have spoke to who moved their child out sooner said they did so because the child was climbing out anyway and they feared for his/her safety.