I've left Sixpence on his mum this year because my other goat came into milk (again) without being asked to and with my hectic lifestyle I didn't want to juggle milking two goats (plus I dno't have storage for that much milk!)
I did milk Mum a couple of times just to see how she'd be (she was fine) and also until he got used to taking milk from both sides of the udder but they've been fine and he's finally weaning off now.
It depends solely on your own personal needs really and also how well mum is adapting to having kids - sometimes you have no choice in the matter!