Back when I worked in land mobile radio, I observed that handheld radio (HT) rechargeable batteries generally had a 3-5 year lifespan, before they were incapable of holding a decent charge. The more abused the battery, the shorter the lifespan. If the battery was taken care of properly, a little longer.
My best HT battery lifespan so far has been 10 years for a Ni-Cd on a milsurp Bendix King PRC-127. That was doing everything by the book, so to speak, and using an aftermarket battery charger/conditioner.
Here are some websites to check out:
Consider how you will be able to power equipment in a long-term grid-down sceneario, and choose appropriately.
HINT: Much of the off-the-shelf stuff you find will be inadequate.