Headlamps need restoring because the clear polycarbonate plastic degrades over time from UV sun rays, road debris, and chemical exposure. This wear strips away the factory protective topcoat, turning the lenses yellow, cloudy, or pitted, which blocks light output and creates unsafe driving conditions.
My process includes using wet and dry sandpaper, starting with 800 grit, and then 1000 grit, 1200 grit, 2000 grit and finally 3000 grit, finishing with a double coat of 3M Clear Coat wipe that protects your lights for between 1-2 years. You can inclease the durability, by not parking in direct sunlight.
Durability can be increased to potenitally "forever" by booking a regular wash, where I add a wax and then a UV protective detailing product every 8-12 weeks.