Most toddlers make the transition from cot to bed between about 18 months and three years. However, there's no specific time that your toddler needs to move to a new bed.It's different for every family.Many parents make the switch when their toddler is able to climb out of the cot, or grows too tall to sleep comfortably.You'll probably be able to tell when your toddler reaches this stage, but you can also check with your health visitor for reassurance.any parents make the switch when their toddler is able to climb out of the cot, or grows too tall to sleep comfortably. You'll probably be able to tell when your toddler reaches this stage, but you can also check with your health visitor for reassurance.