DS (5) has had three sets of grommets. First two sets stayed in place for a year each, third set (incidentaly, done by a registrar rather than a consultant) came out after only a few months. We are desperately trying to reschedule a fourth op - I think it's worth it, but then my DS is also profoundly deaf, so any little bit helps. He has a pair of waterproof hearing aids which he used for swimming, otherwise swimming is a hassle. However, I have read some research saying there wasn't much difference between two groups of children who avoided water in the ears and the other didn't get the same advice. Good luck.