When do you turn the cot bed into the bed?

[Holymoly321]

DS is 20mths and is currently in an ordinary cot. He's getting a bit big for it now, but is still not trying to get out or anything - never really stands up in it at all. Anyway, we're thinking of getting him a bigger bed - probably a cot bed, but wondered at what age do most people turn the DC's cotbed into just the bed.

it really varies. i know people who did it at a year or 18 months.
But we didn't do it to dd's til she was 3.... she was happy in her cot and it just didn't seem necessary.