Given that my original battery is now approaching 6 years old, I'm probably just going to buy the cheapest one, probably the Costco. It seems that I'm driving plenty often enough to keep it charged as I've never had it discharge due to inactivity. I also keep the car in a pretty temperature controlled area (either basement garage at my house or essentially a basement level of a parking deck at work). I expect good life from the replacement as well, given what I've experienced thus far. Keeping a jump pack in the trunk does seem to be a good idea for PHEVs since it is hard to sense 12V battery decline like you can in ICE cars (slow starting).