#i store all of my batteries that aren't in active near-daily use in a lipo bag

[semi-sketchy]

I want to add: if you are putting something with a battery in storage (or just not going to use a battery for awhile), you want it to be around 50% charge. That is the most comfortable place for a lithium-ion battery to be because the battery has two sides: the cathode (discharge) and anode side (charge). At 50%, the ions that move between the two sides and supply power are spread evenly. It'll be less likely (though not impossible) to have issues while in storage.

I have an old 3DS battery I haven't used in 8 or so years stored at about half charge and when I needed it again, it was in pristine condition and still lasted as long as it did when I got that 3DS. Meanwhile camera batteries that I left at full charge were beginning to swell and needed to be disposed of.

For extra safety, take the batteries out of your devices (if possible) and store them separately in something like a Lipo Safe bag (this is a fireproof bag designed for lithium-polymer batteries). Keeping your batteries in one place makes it easier to check them once in awhile for swelling and dispose of them before any accidents can occur. You don't want to find a swollen battery when cleaning out your closet one day (← speaking from experience)

Also PLEASE do not store batteries in something airtight because at that point you are building a bomb.