Not specific to beds as such, but my DD got to around age 7/8 when she developed sensitivities about not having "babyish" things (although I was frequently astonished by the sorts of thing she perceived as being babyish). But even so, 3-4 years is a good run for a bed and then you can either pass it on to another child or i would imagine they hold their resale value pretty well (check out similar beds on ebay, might help you decide).