I used Leatherique products to dye my leather seats and am (mostly) pleased with the results. Like Stroked & Blown, the color match for the dye wasn't quite right but in my case the slight mismatch gives my seats a subtle two-tone effect that I quite like. I refinished the seats three years ago and by far and away most of the dyed areas still look great, the exception being the areas where the original smooth finish had been worn away leaving a rough surface . I cleaned and prepped those areas more aggressively and applied the dye again last year. We'll see how well it holds up this time. In any case, I think that the problem was due to the condition of the leather and not due to any fault in the dye and should not be a problem when applied to vinyl.
cheers - dj