The reason they last that long is that the cartridge draws a very small amount of energy. Most devices draw more power than a gameboy cartridge, so they need a more often change of batteries. That chart shows the discharge for the CR2025, which is the original battery. If you do have to replace it, you can use a larger battery that will last even longer. I used a CR2032, so it will last 1.3 times longer (220mAh instead of 165MAh).