My wife gave me a Torx string (grass) trimmer, as a present. It came
with two, 20 volt battery packs. I now know that I can edge my house
several times. with but one charged battery.

I know that rechargeable batteries have a limited life - attributable
to the number of recharges and years of use. As I will never need to
ever use two packs, what should I do with the likely unused 2nd pack?
I am inclined to leave it uncharged, for _?_ years, until the initial
pack loses the capacity to edge my house.

Would storing that spare battery, in a "hermetically" sealed package
in our refrigerator (or freezer) be a preferred storage option?

Is rthere a different stategy, for the unused pack, that would be
more appropriate? I know that replacement battery packs are $$
expensive.