Thanks for your sharing your experience. This is very disappointing as a year or less is really no longer than potentially applying a standard paint sealant ( or a lens sealant in the cheap headlight restoration kits). From what I have researched here and other boards, Opti-lens is specifically formulated to bond to plastic such that it performs better when the factory clear coat has been fully removed. It there is still factory clear coat on lens (not started to yellow), it is best just to use standard paint coatings (Gloss-coat or Opti-coat pro). I think one the main contributors to lens failure is road rash (mileage with lots of exposure to small rocks). One of the clients I applied Opti-lens to commutes 150 km round trip daily on on the 401 Hwy in Ontario. So we'll see in a year if he experiences the same premature failure that you have experienced.
I know for my personal vehicle (2011 BMW 328xi wagon) I have installed XPEL PPF on the headlight lens to protect from road debris that can lead to clear coat failure on the lens. I wonder if I should be combining Opti-lens with application PPF after 1 week cure time.