Mine is always with me, but when in my truck I put it in the center console. I rotate the ammo to eliminate moisture issues. Never had a misfire though.
This is an odd issue, because the places where it is most likely to be needed are also the places that have the most danger of it being stolen. I've been using an SP101 for this purpose, but have lately been considering switching to something a little cheaper. I've also been considering one of those boys' gun 45LC/.410 combos to keep in the back.