PW3 is it okay to downgrade from 5.15.1 to 5.9.7?

I just jailbroke my PW3 and I see there's a "downgrader" package available.

I'd like to know if it's possible to use that to go back to 5.9.7. This is a fairly old PW3. I got it in 2017. and IIRC it was on 5.7-ish when I bought it. Anyways, after 5.12 the battery of this kindle never lasted the same. It was immediate. The problem only got worse with each new firmware, and I wonder if downgrading is the right option to solve this issue.

Thanks.