I don't know what you have or how many miles are on what you have, but you need to quit buying tires and have the cause looked after. With very few miles on my 2011, I notice signs of tire wear. Both my axles straight from the factory had little to no camber and incorrect toe in ... in fact the front axle was toed out. I had the camber and toe in adjusted per spec locally at Atlas Spring and Axle which Keystone paid for in full. My rig pulls so much better. Some on here have simply had their axles replaced ... to each his own. None the less, you need to have your suspension components professionally looked at before you deplete the local tire inventory
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