Wow! Man you really love that thing! For better or worse thick or thin!!! Hopefully for us that stuff already broke before we bought them.
I would agree with Spraygun that staying on top of your maintenance is key;
Pay attention to your maintenance schedule and make sure you complete everything on time - even a little early doesn't hurt.
I've only put 40,000 miles on my XK in almost 5 years of ownership and a good chunk of that was highway miles and just recently cracked 100,000 miles about 4 months ago;
Most of the issues I had to fix were pre-existing; Fortunately, I haven't had what I would categorize as any major repairs yet; I replaced the actuator motor on my transfer case which was around $750.00 but Chrysler wound up reimbursing me for that repair shortly the P73 campaign was released. Not a concern for you since you don't have 4WD.
The other expensive repair I had was replacing the factory stereo/head unit. Replacing the factory head unit with a new "reconditioned" factory REC unit from Chrysler was around $1,100.00 when it was all said & done, which wound up being a waste of money, as I now have an aftermarket Pioneer head unit.
The only other advice I'd give you if you haven't dome so already, is check and make sure all of your factory recalls & campaigns have been completed; If you haven't done that yet, here is the info on how to do it;
You can check to see if all of the factory recalls & campaigns have been completed for your Commander by clicking on the hyperlink below & plugging in your VIN;
The difference between a safety recall and a campaign is this; a safety recall pertains to a vehicle problem that is a safety concern; a campaign is a vehicle problem that is not a safety concern, but, pertains to customer satisfaction.