I used a tank liner one on a bike, I think the stuff was called "cream" I took my time and folowed the directions to the letter and let everything cure after I coated the insides of the tank, and I had no trouble with it for two years after doing it. I sold the bike and as far as I know it is still fine.
My Buddy rushed his job and the sealant separated from the inside of the tank in I believe 5 months.
How long it lasts all depends on the quality of the work done, if it is done right it should last.
