Its all about prep, and the age of the can you are using- POR 15 has a pretty short shelf life, only about 6 months.
I used their fuel tank repair kit on a motorcycle tank a few years ago and it has held up well. Some people say that you need to keep gas in it to avoid peeling.
I don't think POR-15 is the magic bullet that some people think it is, but it has its place.
