Phone as Hot Spot

A friend of ours used a Motorola Razr for HotSpot for years. After his firs Razr's battery swelled, he started to run you a electric outlet timer that he plugged the wall wart into. It was a simple mechanical time, which he set to shut off multiple times during the day, and then back on. (Don't recall what his pattern of time off/on were.) And he never had a problem with batteries again.

Might be worth a shot to see if that works for you.

Best of luck,
Smitty