I did a trial of the Marvel rechargeables and they never lasted long enough for me. I’d put them on in the morning, and by around 8 p.m., right when I needed them for TV (with the TV streamer), I’d get the low battery warning. Before the trial ended, I ordered the M-312s. Before they came in, we went out of town overnight. Husband and I each had a phone to charge, plus a laptop for him and a tablet for me, and there weren’t enough outlets in the hotel room for everything. BTW, during the trial I also bought the battery pack and returned it a week later. It only lasted 3 days.
I was really glad I had the 312s when we were in the hospital waiting for my first grandchild to be born. She was expected around 8 p.m., so we got to the hospital around 7, but she didn’t arrive until 1 a.m. I had to replace batteries during the wait. If I had the rechargeables, I would’ve had to remember to bring the charger (another big item to fit in my purse), and even if I had access to a plug, I wouldn’t have been able to listen and converse while they charged - DIL’s family had a big baby watch party going on in that waiting room.
Edited to add: I’m connected to either my tablet, phone, or TV streamer the whole time I have the Marvels in. I use the app exclusively to change volume or programs, and stream a lot.