Apart from the rubbing compound which comes with the kit, I haven't applied any form of seal to the headlamps. It's been 5 months now since I used the kit and both my ZT's and my dad's 75's headlamps have stayed perfectly clear. hopefully they last a long time
They've lasted much longer than when I done them by hand using wet and dry sandpaper last year. Started to go back to how they were within a couple of months.