I've done mine with a combination of either wet sanding 1000-2000 grit or buffing with compound.
Mine seem to last about a year either way. This year I just grabbed the buffer and knocked it out in about 5 minutes. I think a lot has to do with how pitted/ crazed they are. The little cracks/ imperfections that I don't sand out seem to re-haze quicker.
I do remember being at a volvo dealership and the dealer flunked another customer's car inspection for hazy lights. He then quoted $500 for new lenses. I wanted to go up to the customer and say... "Psssst... meet me in the back alley in 20 minutes. Bring $50 in cash and we can buff you out"
Probably wouldn't have gone over too well.
