Sweet Willie
You got me worried since we still have about 12 of those 10k certs left (6 each for my wife and I)so I called HHonors and gave them my wife's old account number (as printed on the cert)and it came up as the number of our Mutual account. They confirmed that there still valid, the rule is if you are Silver you can use one against a 100K or higher reward if you are Gold you can use two.
Mike