I’m a skinflint, so I always wanted to be sure that I’d drained each battery completely before I put it in the recycling box. This meant that it I was heading off to a concert, for instance, I’d swap the 312s out for fresh ones, then afterwards, swap them back
And here I thought you lose your skinflint card for using size 312 batteries at all. They cost the same as size 13’s but contain about half the energy.
So how much do you save for all that trouble? If a set of batteries lasted 3 1/2 days on average (died in the middle of the 4th day), you would do 104 battery changes a year, and use 208 batteries. If you decided to change batteries every 3 days instead, so you seldom or never have to change batteries while wearing the aids, you would do 122 battery changes a year, and use 244 batteries. That’s an extra 36 batteries a year. At 25 cents each that’s $9 a year.
Do the same calculation for size 13 batteries that one changes every 7 days, rather than letting them die inconveniently on the 8th day, and it’s around 7 extra batteries a year, costing less than $2 a year.
Do what you like, of course. Some of us hope that we won’t lose the choice of doing what we like, namely using the mature technology of replaceable batteries and not dealing with possible buggy chargers, possible early battery failure, possible unavailability or exorbitant price of backup chargers, etc.