Both of my girls had their crib turned to a toddler bed (just take the front side off) between 20-24 months. Then, both of them moved to a twin bed around 2.5 yrs. I would have never bought a separate toddler bed, but if you have a convertible bed, you can use it to help to transition the child. But, we didn't let them stay in the toddler bed too long, before moving them to a twin bed. And, I think that my youngest, who just went to a twin bed a couple of months ago, she actually sleeps much better now in her twin bed.