I would expect the frame to outlast the unit no matter what the conditions were. Also if the frame was rusted out there would be nothing to weld to for the repairs. The fact that it could be repaired shows that it is not from rusting. Anybody that is having the frame problems should look at the Moreride IS suspension as a fix as it eliminated the small stress area of the leaf spring system.
I had a Thore trailer that was 5 yr old and the frame manufacture took care of the cracks on site in Yuma, AZ at no charge. To say a frame is out of warranty on a manufacture defect in 2 yr is bunk....
especially when DT is touting it has one of the strongest frame on the market.