Thanks for the advice - both of you. I appreciate your insight. I think I'm going to hold on to the car for another year or two, and look for an independent repair shop to handle maintenance issues in the meantime. The only thing that might force me to sell is that I'm considering a job in Salt Lake City, which would obviously mean a lot more winter driving. If this happens, I'll probably go for the 535xi.
Again, thanks for the help - if you have any thoughts, please feel free to share!