I carry the Costco "jump pack" in each car. It's a combination jumpstarter, area light, USB & 12V charger, and air compressor. The older one is in my wife's car and still works at five years old, although that's about as long as I expect one to last.

You must charge it every month; I have a battery maintenance routine that includes this. I cannot count how many self-saves and wow-that-was-easier-than-jumper-cables saves I have had with them.