The key to these things is maintaining them between 50F - 70F; people leaving them in their trunks or gloveboxes in the blazing sun or freezing winter nights drains the battery & considerably shortens its functionality & useful lifespan. Properly cared for, they will last for years & imho pay for themselves in the first use. Don't have to pay $75 for a tow truck to come jump you, or wait for one to arrive, if you have insurance. Neither do you have to lug around jumper cables or search for someone/wait for someone to give you jump. Important peace of mind if/when your car won't start. Back on the road inside of 10 minutes. The other pieces of kit for a car would be a cigarette lighter tire inflator & a tire patch kit. WAs in the Boy Scouts; all about being prepared. You could drop me in the middle of the wilderness & I will survive. I have my emergency duffel containing room for a couple weapons, ammo, knife, hatchet, lighters, tinder, clothing, spade, tent etc. Hit the door with that motherfucker inside of a minute if need be.