My son is about to turn a year old. While I know he's not quite ready for his 4-in-1 crib to be converted into a toddler bed, especially since he's only just started walking steadily on his own, I was wondering when you changed your crib into a toddler bed (with the toddler rails, sold separately)? Was it at a certain age (18 months) or a certain milestone? What were the signs that told you your LO was big enough for the switch?