Quoted By:
They'll last longer than you will barring physical decay, absolute loss of power in the flash memory cells or random bit flips leading to data corruption caused by radiation. Turn on the GBA with your cartridge every few months for a couple minutes. It'll take a VERY long time for the memory cells to completely bleed dry considering how low capacity they are (likely decades) but it can and will eventually happen if you completely neglect your cartridges.