Like every paint job, the results will depend on how well you prepare the surfaces you are painting. SEM is not actually paint, it is a flexible coating that will be drawn into whatever you are trying to re-color. Is it any good? I think it's the best stuff on the market. Just be sure to use all SEM cleaners and prep products and follow the directions to the letter. If you do, you will end up with a great job. If you don't, not so much. Remember, this is a coating, it will not make your old vinyl new again, it will only change the color of what you are coloring.
No one lives forever, the trick is creating something that will.