A long time. However, there are factors that will affect just how long it will last, i.e., weather, maintenance, etc. I can tell you it creates a deeper, richer sheen that penetrates deeper than nearly all other trim products and will transform your trim to new condition - not like new, or nearly new, but literally new condition. You can also dial in the appearance from shiny to satin to matte just by how much you wipe off before it cures. There are 2 flavors... one is for returning black trim to its original dark black condition and one that's on the gray side for trim and plastic that wasn't black to begin with.
Check out the vids on YT to get a better perspective and to know what to expect. It's a little pricey but a little bit goes an unbelievably looooooooooong way. No, seriously!