I have Oticon Opn 2 miniRITE T hearing aids. When Costco switched manufacturers about a year or two ago (not sure how long it has been) I could no longer use the Costco batteries. They had worked fine and been great with the previous manufacturer. I am so disappointed they changed manufacturer.
I have the same issues where the battery could last two hours or a couple days but never consistent and for a full five days like I had been used to.
I have switched to buying my batteries from Sam’s Club for a similar price to Costco and they last a normal amount of time. I do switch my batteries between my left hearing aid and right hearing aid each morning when I put them in so they end up running out about the same time.
I thought it was just me that had issues with the Costco HA batteries, nice to know it is not just me.