As my dad used to say "Everything's made for a price" ...meaning design & materials are limited by the market; competition, etc. A well made flatbed trailer should last 40 years, with maintenance (brake maintenance/replacement, and new floor eventually)...but most livestock trailers seem built to throw away, for the very kind of thing you mention.

The 1" tubing that housed electrical wiring to cross under the floor near the wheels rusted and just fell off one day (light tubing, and only tack welded to the frame) I had to replace it (and wiring) with something heavier. The axle mounting may not be much better...thanks, I'll give it a hard look.