I have personally constructed a large 5metre wide by 10 metre deep pool of water in my spare room, covered by a light fabic attached to a pully system. I rest the lipos on the fabric, if theres a fire the fabric will burn quickly dropping the lipos into the pool of water and the pully system will cover it over with a 1 foot thick metal cover.
I will then run for cover in my underground bunker for 3months, eating baked beans from tins, assuming the lipos have burnt the entire earths surface.
The above may or may not be the true.
seriously, if you're worried, check the batteries for any swelling, if they feel a little 'puffy' get rid and buy some new ones. Keep them stored at a storage charge and in a bag, unless they're damaged in the first place you'll be fine.