Originally posted by Takata
The manufacturer opinion is that the pinger signal is expected to fade very quickly after operating for 30 days
This is because of the properties of the lithium battery, I think. The nominal voltage stays the same for the specified 30 days and then some, but once the voltage starts to drop, the drop is rather dramatic and therefore the beacon stops sending any acoustic output at some point, rather sooner than later.
Extended battery life would not be too difficult to achieve. Another 200 grams of additional weight perhaps. Peanuts, really.