My brother's watch lasted a decade on the original battery, and these batteries are tiny, so I'm just wondering.... how long with a big enough battery could one last? : r/casio
Casio MQ-24 series watch battery replacement – Jeff Werner
Amazon.com : Synergy Digital Camera Battery, Compatible with Casio Exilim EX-S770 Digital Camera, (li-ion, 3.7V, 630 mAh) Ultra High Capacity, Replacement for Casio NP-20 Battery : Electronics