Remember, it's not two years from the date of purchase either, so it's all an approximation. I have had a couple that have lasted much, much less for the ride photos without the touch points (like 7DMT), one was a limited edition that was released originally about a year earlier (who knows when they were manufactured), but it didn't last much longer. These days, I tend to just wear the newest free one or switch out the puck.
I don't know if it would make any difference, but would having a new, activated band linked to your account in your pocket or back pack help establish a redundancy (where even if it doesn't pick up the older one on your wrist, it could still interact with the newer one in your pocket and link up photos)? If so, that could help out people who might like their older one and don't have a newer puck that would match it as a replacement, or those that have a special edition (like the last Epcot anniversary ones) that do a special effect at the touch points (light up in a unique color pattern and/or sound) but don't have the juice left to interact with the remote sensor ride photo systems.