As with anything that is electrical in nature a lot of it comes down to how well it was made and how well it is cared for. A cheaply made watch will not last as long as a more expensive quality made a watch in most cases. Also, if you are not taking care of your watch and are using it in a way or in conditions that can damage it, then it will not last as long either.
When all is good and done correctly, a good altimeter watch should easily last you 3-5 years or more!