Fully charged lipos, any chemistry, can sit for a good long while with very small effects. Caveat: we tend to over charge our lipos, but not enough to damage anything short term. If you leave one alone charged for maybe six months it will have reduced capacity, just like leaving it empty for 6 months. Outside in an ammo box, it'll sit for a week easy, but probably needs to be warmed up before use. On a winter day, I keep mine in my shirt pocket under my coat walking over to the school. Should be safe enough