My 2011 headlights still look brand new (except for a few minor chips and pits). They get a combination of treatments throughout the year so I'm not sure what to give he credit to.
I use blue magic headlight lens sealant a few times per year, maybe twice
I wax them with the rest of the truck 1-2 times per year
When I hand wash the truck they get waxed with d156 spray wax. This used to be almost weekly but I just won't have time for that anymore