My boys were bf so never really drank from a bottle. They started on EBM from a sippy cup at around 5 or 6 months because they wouldn't drink from a bottle. The other kids at day care mostly seem to stop bottles not long after 12 months but some still have them long after that. I think the main reason for stopping bottles is that it does increase the risk of cavities, but it every child is different so there is no golden rule. I would say that if your child will drink from a sippy cup it is better to get rid of the bottles, but if they aren't then you can take longer to transition them. GL with whatever you decide to do.