This battery lasts the life of the router under the operating environmental conditions specified for the router, and is not field-replaceable.
But who determines its lifespan?
Knowing there is a battery set to fail and I can't simply replace it makes me physically uncomfortable. Enough so that I'd rather it not have RTC.
Thanks Cisco.
Some true asshole manufacturers store critical data in a prom. They solder the batteries in and if you remove them and it loses power the prom clears bricking the device. C/KU band satellite receivers do this. As well as many older cable tv boxes. I used to repair them and had bench power supplies to keep the prom alive during repair. At the end of my run with the cable industry I had started cloning the proms and replacing the information that they stored there.