My son stayed in his crib until right before his 3rd birthday that I had his sister. He was 2 when he got out of the crib, but I always left the railing down, and the mattress was all the way down to the lowest so that he won't break his head when he got out. I always told him when he woke up to call me and he did. He was pretty independent at 3 yrs old and was potty trained, so he was a lot of help. Don't force the potty training...it'll just make you frustrated...and each child learns at their own pace. I wouldn't rush the big boy bed either. I used his crib for his sister and he never felt any resentment or replacement. He was and still is a great big brother.