We put the older two into a single bed when they were around two as we needed to kick them out of the cot for the next baby LOL and #3 went in about the same time, I think it was probbly 22mths - she wasn't actually two yet anyway. #4 will be in the cot for a fair while longer I reckon and he's 2 next month. He's just not ready for a bed - we tried taking the sides off his cot a few weeks ago and he wouldn't have a bar of it, plus he's a really restless sleeper and he would just fall out.