Casio watch. Had it for ~20yrs. It died today but I just replaced the battery and it's back again! I had only changed batteries twice: 10 yrs ago and today. Truly BIFL
Casio MQ-24 series watch battery replacement – Jeff Werner
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 10-Year battery? | WatchUSeek Watch Forums
Casio MQ-24 series watch battery replacement – Jeff Werner
New Replacement Watch Battery for Casio G-Shock Models GB-5600 GB-6900 GB-X6900 | eBay