tire wear and axles

I had a crossroads cruiser fiver with 15" and 8 ply tires. Had several tire wear problems and had some alignment done and still was having problems. So I decided to trade and I got a new Jayco Eagle with 16" and 10 ply tires with Dexter axles. I just noticed the left rear tire seeming to be wearing on the inside but not badly yet but enough to notice. Now I estimate about 7000 miles put on the trailer since purchase. Now this is my 3rd fiver and the first one did not have any axle problems. However I was not retired yet and not doing wintering down south so I was not putting on a lot of miles and not going cross country. So I bought my second rv (cruiser) and that winter went to Florida for the winter and then the tire wear started. I get my 3rd fiver (Eagle) and winter in Arizona and Texas and put on maybe 7000 miles and the tire wear seems to be starting. I have gone into these forums and talked about axles and gotten advise from replacing axles because you don't align axles or you align axles and put on good tires. Here is the bottom line question: Is this the nature of the beast with pulling a trailer whether it is a fiver or tt, is this wear expected because of going cross country? I don't seem to hear this problem with motorhomes. I am getting the feeling that this is going to happen with trailers. I am very careful about tire pressure, I only travel down the road at 60 miles per hour, I slow way down for railroad tracks and I do not bump curbs. Any more help would be great!!!
Thanks, Bill