They are part of the set so I doubt it's possible! Judging by the number they give you, they must be expecting you to replace them after every other battery change, which for us with the lithium batteries is about every 6 months. I think you need to replace them for waterproofing reasons; the Combo is rated IPX8 which means it is waterproof, but only to the limit that it has been tested (and presumably they haven't tested it for an hour in a swimming pool, hence they tell you to take it off for swimming. I think it is probably more waterproof than they let on though, I know of at least one person who went swimming and forgot to take theirs off, and it was perfectly fine afterwards!)
