It's hard to know. They are all different. We moved DS1 into a big bed at around 16 months as DS2 was on the way. It went really smoothly, no problems at all. DS2 is still in a cot at 20 months, and we will be converting his cot to a bed soon, but I think it will harder than with DS1. DS2 is a great sleeper, but not good at the staying still thing. So it will be interesting to see how he goes when he can climb out of bed.

I think the best thing you can do is try it and see how it goes. If it really doesn't work, you can go back to the cot. Remember to give them plenty of time to get used to the idea. Talk up the "big boy bed" for a few days and maybe get him to pick his own linen. GL.