Good to know Bowgie, thanks. Do you (or anyone) know if the certificate is considered redeemed if you make a reservation? I know the terms say "Free night award will expire one (1) year after the date of issuance.".....so if my one year is on August 31 and I make a reservation today for September 07....will it impload before I arrive for my stay?

No. It must be used = redeemed = stay at the property by the time that it expires, not when a reservation is made.

So, to answer your question, yes, it will implode before you have a chance to use it. You can use it up through and including 8/31 and no later, unless you somehow get it extended.

The reward regardless which instrument you use, is from the SAME inventory, i.e. rooms set aside for reward redemption.

You need to get an extension from Marriott AHEAD of your stay. Otherwise you would find yourself have no valid cert to pay for the room. Cert must be valid on the date of arrival. That is how the hotel gets paid, via Marriott Rewards.