Im talking about the battery backups used to save games. How long will they last? I just bought a Genesis with some older RPGs Also if the games arent heavily used does that mean the batteries will last longer?

I’d just throw a guess of about 10 years out there. I’ve had games die much sooner and last longer though it really depends on what kind of battery they’re using mostly. Eventually the battery will die though but if you’re feeling brave it’s not too hard to open up a cartridge and replace the battery, they tend to use the disc like hearing aid style batteries.