Is it too early to train my 19 month old to sleep in a toddler bed?

Both of my babies went into toddler beds at 13 months. I waited about a month after their first birthday. I plan on putting our third child straight into a twin bed as soon as they are able to walk stable enough to get out of bed. This way I can do bunk beds in one of the rooms. 18 months is definitely old enough. My son just turned 3 and we are really wishing we would have just put him in a twin bed, he is pretty tall and if he didn't sleep curled up I would have moved him to a twin bed already. I'm hoping he can wait a couple of months. My advice is, if you haven't already bought a toddler bed, don't waste the money. These kids grow so quickly you might want to just buy a twin. If you do buy a toddler bed, buy a used one on craigslist. Don't pay a ton for something you will not be using very long at all.