my copy of pokemon silver cartridge shipped with a bad save battery. i'd only be able to get to the fourth gym or so before the batteries in my gameboy would die.
Revive your dead Game Boy cartridges with a new battery - Make:
How to replace a GameBoy cartridge battery without losing saved data
How long do the batteries in an original Gameboy and color cartridge last? - Quora
Just installed some Gameboy game battery holders I ordered for cheap from China. No need for tabbed coin cells anymore! : r/Gameboy
Give Your Classic Pokémon Eternal Life with This Game Boy Cartridge FRAM Mod - Hackster.io
How to make your old Game Boy as good as (or better than) new | Ars Technica