That's great and most if not all of us get likewise if we've had Marriott Visa activity but I think the OP is asking about extending not the yearly cert from Visa but the limited duration last megabonus cert which specifically stated in the promo as being not extendable
Originally Posted by
beltway
I've repeatedly extended anniversary certs, always receiving a one-year extension from the date of the request (so best to call shortly before the original expiry). You can do this only once for a given cert.