If someone said a shirt will last for years I would have a different impression than if someone said that a battery-powered thing will last for years.

For example, I have motion sensors in my home and I have to replace the batteries from time to time. If the manual said "the batteries last for years, depending on usage" I would not be surprised if it lasted for 2 years.

Here, it sounds like the battery life will vary greatly based on usage. In fact, it sounds like the battery life is almost entirely a function of how much you use it. It would be interesting to know how much the battery will drain over time if you don't use it, but of course we can't know this for certain before this has been in the wild for years.