Corect me if I'm wrong, but a CERF is only valid for one year. I believe I read that on the OFA website, or the link to the eye information. Now, I guess if you have it doen twice and nothing comes up, then you can probably say yes, my dog is clear. But the actual certification is only valid for a year.
***If the dog is certified to be free of heritable eye disease, you can then send in the completed owner's copy of the CERF form with the appropriate fee ($10.50 for the original CERF Registration, or $8.00 if it is a recertification). CERF has adopted a policy effective Jan. 1st, 2001 (by post mark) that a permanent identification in the form of microchip, tattoo or DNA profile will be needed for any dog to be registered with CERF. The certification is good for 12 months from the date of the exam and afterwards the dog must be reexamined and recertified to maintain its' registration with CERF. *** from the Cerf page
CERF - Canine Eye Registration Foundation
Dawn