D.T.
Hi C.,
I am the Mom of 3 and one on the way. I got the BEST advice from my next door neighbor......don't move them from the crib until they don't fit anymore. I followed this and ALL my kids still napped till 3-1/2 years old. I have done this with all my kids and they do great....all my friends are AMAZED that they sleep so well. This was the secret!
Otherwise yes I agree go to a twin with sides, what's the point of a toddler bed when it is the same size mattress as the crib just adds freedom to get in and out. Good Luck hope this helps.