When M was about 2 years old, we moved her out of the crib and into the toddler bed. She wasn’t climbing out of the crib or anything, but we knew we’d be needing the crib for the new baby (S!). We wanted to be sure those two things (getting kicked out of your crib and getting a little sister) were two unrelated things, so we made the transition with lots of time to spare. It went really well. We’ve been offering her a twin size bed for a while, but she’s said she’s fine with her little bed. It seems that as soon as she turned four she decided she’s ready. This transition was absolutely seamless and we really love having the bigger bed so we can really cuddle up with her at bedtime.