If you're talking about the Level 3 Certificates (i.e. reggie reps) then they are valid indefinitely as long as you are FSA registered with your firm. If you are not on the register for more than a year (i.e. considered to be out of the business) then you have to retake them. That's what I've always been told anyway, could be wrong.
I havent heard that one, the certs are still valid as qualifications, although your firm may insist that you re-take if they feel it necessary as part of their due diligence for the FSA reg