Kids become attached to their stuff, especially if they've had something for as long as they can remember. Your little guy might develop a fierce devotion to his toddler bed, insisting on sleeping in it even when you think it's high time to get some grown-up furniture in his room. Toddler beds use a standard crib mattress, so he won't fit in it forever. Most toddler beds do have weight limits and height restrictions, which will eventually force him into a big-boy bed.
It's not comfortable to sleep with your feet hanging off the end of the mattress, as any really tall person can tell you. Toddler beds use crib mattresses, which normally measure around 52 inches long. Your kid could be well into grade school before he outgrows the bed strictly using height limitations, since most kids don't reach that height until around age 9, according to the Centers for Disease Control and Prevention. He's more likely to surpass the weight limit first. If he doesn't, the narrowness of the crib mattress -- around 28 inches wide -- will probably push him out of the bed -- literally.
A toddler bed was never meant to support the weight of a big kid. You might have already have discovered this if you've ever sat on the edge of your child's toddler bed. The Consumer Product Safety Commission defines toddler beds as holding up to 50 pounds. According to CDC height and weight charts, the average child doesn't reach 50 pounds until around age 7, but your kiddo might not be average, so move him before he collapses the bed in the middle of the night.
By age 5, your getting-older-by-the-minute little guy may be ready to say goodbye to the toddler bed and shop for more grown-up furniture. The name "toddler bed" gives a hint about the suggested age limits for its usefulness: it's for toddlers, which means up until preschool age. The CPSC describes toddler beds as reasonably expected for use by children under age 5. If he's hesitant to move up to an adult-sized bed, keep calling his current bed a "toddler bed" in his presence. Most kids don't to want anything that seems at all babyish, so he might start to protest having to sleep in it.
Life Without Side Rails
The move to a full-size bed introduces your child to life without side rails -- and the possibility of ending up on the floor sometime during the night. For this reason, moving from a toddler bed to the top of a bunk bed isn't a good idea, even if the bunk bed has side rails on it. Keep him down to earth while he adjusts to his new bed. The American Academy of Pediatrics recommends not moving children to a top bunk until they're at least 6 years old.