Hello joe....
AZ , and tx sun will ruin paint as we know....sounds like your prep was flawed and the paint was not top notch. I have 2 vehicles painted with PPG Delstar in the 80s.....one a 53 studebaker bonniville show car and a 69 dodge P/U , both still in perfect condition. Yes, the stud is always garaged , the truck always outdoors.
Point, the prep is the upmost important, and the quality of the paint next. However, some surfaces should be primed with EPOXY PRIMER...PPG DP 40 is one....once dryed you cannot even scrap it off.....even off concrete.....dont get it on you either.
Clear coat is great but all paint has to have a UV resistance......Base coat /clear coat is probably more critical....of course, thats what factory paint jobs are...non metalic paints are also more resistance to UV.
tom