Big bed at around 15 months here.. I think.. (or as soon as they knew how to climb off the bed) But that is from co-sleeping in our big bed, not from a cot, so nothing daunting about it being a big bed. We did use a rail for a while. They could then bring themselves in to us when they woke up during the night

I'm of the opinion that toddler beds are a waste of money too.. but probably depends on the child too.