I don't think his empty 7000# landscape trailer weighs 2500#. He did not say how big it is, etc. but most are around 1500#.
Messmaker, what kind of tires have you been using? If you are getting "bias ply" tires, it is not surprising that they don't last long. They are cheap tires meant for trailer owners who don't use their trailer much, like a guy who hauls his boat to the lake a few times a year. If you use yours often, buy radial tires. They will last much longer. I put new radials on my 6x12 3550# last year, have towed it a few thousand miles since then, always loaded to capacity, and the tires still look new.
Are your tires wearing out evenly across the width of the tread, or are you wearing the center out first, or the sides out first? If the center wears out early, your tire pressure is high and this causes the center wear. If you wear the sides first, probably the opposite problem. If your tire pressure is way too low, the tire will deform a lot under load and this makes it flex more as it rolls, creating extra heat, and causing the whole thing to wear out very fast.