I finally had to replace the (second) battery on my K3S yellow which I've used for nearly a year. The date I marked on the cell was 4-26. Not bad for being used around the house every evening and many a night. If I was to spitball an average daily run time, I'd say 3 minutes. 7-1/2 months is 225 days, so 675 min.. divide by 12... 56 hours give or take.