Reading this I am wondering if the salt water in FL is different than the salt water in CA....
I've had a steel non galvanized trailer last me many years, with many miles, and many a salt water dunking.... But, I will say when I got the trailer home, it did get pressure washed and rinsed with soap and hot water....
That is an interesting point... I would suspect the salinity varies a bit between ocean and Gulf. Perhaps the biggest reason would be the ambient temperature of both air and sea? Higher temps would accellerate the attack on the spring steel?
Checking the mattress for enough dollars to switch to a torsion bar...