I've had problems with mine too. I need to keep a better eye on my tire pressure. I now keep my portable air tank hanging in the pole barn next to my tractor. Usually if I don't check the pressure every month or so, I end up having to bring it to a local garage for them to clean up the rim & re-seat the tire.
It always seems to happen at the worst time too. One time it happened on a Saturday afternoon when I was 1/2 mile off the the road. I ran down to the house, grabbed my ATV and a set of sockets & a breaker bar. I made it to the local garage just as they were closing. The mud had frozen to the inside of the rim, so they had to break it down to clean it up. The tractor might have had to spend the weekend in the woods if I the garage hadn't been open.
I am actually thinking of getting an entire rim & tire for a spare. I figure when I get a new set of front tires, I'll keep one of the old ones mounted and buy an extra rim.