There is no definitive answer to this question, as the lifespan of CO2 canisters in soda makers depends on a variety of factors. In general, however, CO2 canisters will last for a few months to a year or more, depending on how frequently they are used. Factors such as the size and shape of the canister, environmental conditions such as temperature and humidity levels, and usage patterns can all affect how quickly CO2 is released from the canister. Additionally, some soda makers automatically notify you when it's time to replace the carbonator, allowing you to easily keep track of your canisters' useful lives. Overall, there is no one-size-fits-all answer to this question; different CO2 canisters will last for varying lengths of time in different soda makers. However, with proper care and maintenance, most canisters will allow you plenty of enjoyment from your favorite sparkling drinks for many months to come.