A BBSHD should be good for about five times that number of miles before you need to open it up and service it. Seems really unusual you are having that happen. I have several bikes I switch back and forth with so my mileage on individual motors tends to be rather low. But one of my daily drivers is at 4400 miles and I've never opened it up. I have several others ranging from about 1000 to 2200 miles and same story. If you are pedaling a lot, the clutches tend to wear out but that the most common wear item and its cheap to replace.
If all you know is what you can do on the displays, you haven't even scratched the surface. Yes I recommend strongly you tune the motor. Follow that link I gave you above, and maybe also follow the link in that article where it goes back to the original 2021 article I wrote that tries to explain every single feature. BUT the 2023 version benefits from a lot of trial/error and a better understanding about how features interact.
I buy my motors from Luna Cycle. Best price and they use a reliable, powerful 30a firmware version that works perfectly with 52v packs. Bicycle Motorworks sells quality packs that have BMS' strong enough to handle a BBSHD without issue. California Ebike sells motors but they use newer Bafang-approved firmware that limits 52v motors to 28a. There's no reason to do that Bafang is just being pissy about the fact that they don't sell 52v and want people to buy their batteries.
Technically, yes a 52v system has more power. But its only a small amount. The real reason you go to 52v is the larger usable voltage range that lets you operate the motor for a longer period of time.