Average life span for trailer tires?

3 - 5 years depending upon exposure to sun. Cover the tires and take the camper on the road a few times in the winter months too, to keep the tires healthy, they'll last longer. Dry rot is the worst enemy. The more you can keep the tires rolling, the better they stay.

I hitch up about once a month in the winter months and go for a 20 - 30 mile drive. I think this has attributed to my tire longevity (6 years on my previous camper from the time I purchased it).