I had my boys in playpens and it was a Godsend. About 1 month was all they lasted though. They learned how to climb out. My oldest son was in a twin bed at 11months because he was climbing out of his crib. When the youngest was 13 months he was in the crib getting ready to climb out and it collapsed around him. The youngest was the 3rd to use that crib. My niece used it and she used to rock it across the floor and push the lock on the bedroom door. Took the lock off and put her into a twin. She was about 14 months.