Just adding my own 2-cents’ worth here. I’m one full week into a trial with the Marvel for size 312 battery. I stream about 2 hours of TV a night, and only the occasional phone call - that’s pretty much it! (No streaming of music from phone or laptop, etc.,)
My 312 batteries last about 3.5 days. That means first thing in the morning on Day 4, I just go ahead and change the battery. It drives me NUTS when a battery goes dead half-way through the day - and who knows where I’ll be? On the phone? Driving the car? At a doctor’s app’t?
No, I’ll just try to make sure that never happens and have the batteries already replaced on a regular schedule. I actually keep a pocket-sized calendar in my wallet with the day marked when I change my batteries, cuz once in a while, I simply can’t remember: Was it last Sunday? Maybe first thing Monday?
As a point of comparison, the size 13 batteries on my Phonak Audeo B-Direct aids last 4.5 days. So I change them the morning of Day 5.