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.
Relevant fact: Most standard non-letter batteries are named after their physical size, for example a CR2032 is 20mm diameter x 3.2mm height; or not a button battery, but an 18650 is 18mm diameter x 65.0mm height.