I had used Trinidad for several years, and normally was getting three years from it. ( New Orleans area ) After the oil spill last year ruined the Trinidad, I tried some stuff made in Florida. Super Ship Bottom.
It's a hard ablative, and the mfgs. tell me it will go three years, with two coats. It's 129 per gallon, which is a long way from Trinidad pricing. Has only been on for a little over a year, but so far so good.