Each child is different, some are ready fairly early and the others not til 2-3. My son for one never slept in a crib, he hated it. He would be dead asleep and once his body hit that crib he would wake up. We co-slept with him and when he was about 9 months we just got a full sized mattress on the floor, totally babyproofed his room and babygated it at night and during naps. My daughter moved into her twin bed when she was 18 months and transitioned from the crib to a bed without problems. I think it is kind of like blankies and pacifiers its a comfort thing for some and they might not be ready to move out til they are older. Climbing out of the crib and such like that is a huge indicator to get them into a bed, but if they love the crib then there is no need to rush them out unless they want a big bed. I agree toddler beds are a waste of money go straight to a twin. I just have the box spring and the mattress on the floor i dont even use the rail thing, i think i heard a thud once from her falling out and she just got right back in and went back to sleep. Just go with what you think your son can handle.