I have had a rim failure, on one of my old mountain bikes, and it's not something I would necessarily choose to experience again. The sidewall of the rim had been worn so thin that the pressure of the tyre (combined with a particularly gnarly and rocky descent just peeled it away from the rest of the rim. Can't say the 11 mile walk home in cycling shoes was great fun!
Obviously, it is possible to spend ridiculous amounts on new wheelsets, but
Wiggle have got some great deals on lower end wheels right now.
7,000 miles from a rim sounds fair to me, and it certainly doesn't owe you anything after that kind of service. Personally, I think I would find a pair of wheels at a good deal and be satisfied that the rims and hubs we're going to be good for another few thousand miles. Peace of mind, and for sure, if your current rim does fail, you can bet it will be miles from home on the wettest day of the year!
I got away with it pretty cheaply (apart from the long walk), but there is also the danger aspect if the failure is catastrophic.