Yeah, I may end up switching to Verizon, though I'm not sure how happy they will be. US Cellular owns the towers near me and Verizon has an agreement to share towers with them. However, Verizon recently cut about 12,500 people off because they were using non-Verizon towers too often. (This made some news sites and the municipalities are less than impressed.)
US Cellular doesn't like to activate non-branded phones, though I guess they have started doing some. They share the same tech so I don't know of any technical limitations that would prevent it.
I will need to replace mine. It is running 8 (.1 maybe?) and I guess it can be upgraded but I'd rather not risk it and it is getting long in the tooth.
I should add that I'm in an unusual position where I don't even carry my cell phone very often. I often even forget to bring it with me. I don't depend on it, am not chained to it, and it frequently goes without attention for days or weeks at a time. I don't actually install anything on it. The stock apps do everything I want to do, and more. Right now, I think it's in the cab of the tractor, though it might be in the car.