When I purchased the pontoon boat August of 2011, I purchased two 6-gallon portable gas tanks. You know, the typical red plastic 6-gallon things. A the end of 2013 season I noticed both tanks were starting to turn white where they were most exposed to the sun and were developing cracks. They are both mounted out in the open on the stern of the boat. I sent a picture to the manufacturer who replaced both tanks under warranty and asked me to ship one tank back to their quality control dept. So...5 years later the two replacement tanks are doing the same thing. In addtion to the cracks developing, the white areas are starting the flake off. The plalstic under the white areas that flakes off seems OK. I'm going to replace both tanks for the 2019 season.
I'm not mentioning the manufacturer's name because they stood behind the tanks the first time. I read somewhere the expected life of a plastic tank is ten years, but I seem to be getting 1/2 of that. I would buy a metal tank, but they no longer seem to be available. I'm not having custom aluminum tanks welded because I need to be able to carry the things to the local gas station and It would probably be very expensive.
I might also mention these are EPA low permeability tanks that don't vent. They blow up like balloons which as I look around is the norm for unvented plastic tanks.
I'm wondering about other boaters experience with plastic tanks?