Per Stormin Mormon:
But, I do like to keep the
options open. I can stop by the store and buy AA cells
easier than finding a lithium ion battery pack.

I have become partial to AA alkaline over Li for infrequently-used
devices.

Yes, Li offers exceptional shelf life.... but alkalines have a shelf
life of something like 5 years while my wife's phone (which she refuses
to use on any regular basis, but thinks the needs to have...) comes up
dead after a few months if it has not been charged.
--
Pete Cresswell