Itās quite freeing to not worry about battery life anymore, but if everything works and you have all the security releases with 15.7 then just stay there. If thereās no features you need on 16 then just stay put.
You canāt go back if you upgrade, so doing nothing is just fine.
If battery life is a concern at the moment, then a 6.1ā 14 or 15 is in your future. I have a 6.1ā device and itās nice to not always being concerned with battery life.
But I was certainly fine with the battery life on the 13mini on 16, so consider just upgrading and not worrying about it anymore