A.S.
I think the younger you transition them to the "big bed" the better. My husband and I were living in NYC in a 1 bedroom so my son was also in a playpen until he was fifteen months in the same bedroom. When we moved here to boise, instead of buying him a crib we just moved him into a twin bed with a rail on it. He had a hard time adjusting for like a week, and then he finally started sleeping through the night for the first time and he took much better naps! I hope this helps & good luck!