When we got our rig 2 years ago, I replaced the tires. The old ones looked good but the sidewalks were cracking.
Put a couple thousand miles on them and then left for an 8,500 trip. About 7,000 miles in I noticed that all 4 tires were very worn on the inside. So much so that I stopped at Les Schwab in Toolee, Utah to have them flip all 4 tires so the worn edge was on the outside. They were nice enough to let us boondock under their carport for the night.
When we got home I got into it. First, the rig came with 6,000 pound axles but the springs were rated 2,500 pounds. I swapped out the springs to 3,000 pound rating.
You can check out alignment with an 8 foot straight edge. Place it horizontally along the center of the tires. The sides of both tires should be touching the straight edge at all 4 spots. If not, axles are bent. My left side was fine, but both tires on the right side were off. If you Google "straighten trailer axle" you'll find videos of guys using a chain and hydraulic bottle jacks to straighten bent axles. I spent $32 for a 30 ton bottle jack at Harbor Freight. Followed the videos and aligned myself. You can check vertical alignment using a level, they should all be slightly "bubble out".
Leaving on another cross country trip next month. Put on new tires and am going to keep an eye on tire wear using a tire depth gauge.
'05 F250 6.0 Bullet Proofed
'02 Montana 3280RL Upgraded a bunch.