What's the cost of your hearing aids?
How many 'hearphones' could you have for, say, 50% of that cost.
10 hour of hearing seems close enough to a day's usage, perhaps a bit shy but probably not by much. Certainly two recharged pairs should see you through a day.
How much charge do they need - or rather, what's the size of a recharge battery pack, and how would you compare the cap-ex of your hearing aids versus the cost /convenience trade-offs of an alternative?