I DO have a convertible crib so I'm set for beds etc with Elyse now forever.. honestly I love the idea of this, the crib is gorgeous and I thought even if we decide to get her a new bed when we move because this one doesn't match her bedroom decor, or for whatever reason.. that we could a) save the crib for another baby, or b) put the bed into a guest bedroom, as it's a double bed.
I would say it depends on the crib and child (size of child, height of crib, if the child figures out how to climb out/lower the side, etc.)
But I think Elyse will probably be in her crib until she's about 2? My little cousin is still in her crib and she is 28 months old I think..