theotherjonv – my girl hated pooing and when she was 3-6 months old only used to go if she was sat on my lap and I rubbed her back.
I broke my hip and was in hospital for 3 days and she refused to go.
Within minutes of arriving home I had a lap covered in 3 days of soggy poo that had exploded out of every seam of the nappy.
She did decide at 18 months that she was too big for nappies and had two accidents in the night subsequently but was otherwise fine.
My son had freinds who still wore nappies overnight at 6, though, so it's down to the individual child.