I dunno. Maybe I’m an outlier here, but I say CHARGE 'EM UP every single night. Yes, just put the aids in the charging base - don’t even turn them OFF - just drop them into the charger overnight.
Why? Cuz for starters, if you have a pet at home, they’d be less likely to grab one aid and EAT IT (as happened to me years ago when I had one of my battery aids on the nightstand at in-laws eaten by the DOG).
Also, considering that Phonak swaps in a NEW rechargeable battery before the warranty is up (in 3 yrs), you can have your rechargeables replaced, no questions asked. Run 'em into the ground. Use 'em! Hearing aids aren’t like UV wands, massagers, or other devices that will likely fail due to a “rechargeable” battery that no longer holds a charge. These are medical devices. We wear them cuz we NEED to wear them.
Finally, if you live in a place where you may have power outages for days or perhaps the power supply is unreliable, you’d always have that many more hours of use in an emergency to hatch Plan B. (perhaps involving battery-operated aids)
With my hearing loss, I’d never start a day with less than 100% charge in my rechargeables. If my aids no longer held a charge, they’d be sent in to Phonak asap. That’s why I keep backup pairs on hand. Well, actually, I went back to using 312-battery aids full time last spring, but that’s a whole 'nuther topic.