I've noticed that mine only seem to remain truly clear and sharp for one season. I don't like to ride with a dirty shield, and even minor scratches distract me, and the Pinlock seems to take on a slight haze to it after a season of use. Not bad, just not 'new' looking. But it really isn't so dear that replacing it once a year becomes a major issue. Pinlock certainly is the best to come along so far! The 'Clarity Defogger' drops really work nicely provided you put them on every other day or so, but the Pinlock requires no such maintenance and do a perfect job.
Stitchawl