The hotel voucher is electronic and either doesn't expire (according to Chris) or can be extended indefinitely for free.

As of October 2007 you have to have a hotel reservation to which you attach the 7-night hotel certificate, even if it is a dummy reservation just to hold the certificate. Chris told us a couple months ago that they intend on fixing this, so you won't have to have a reservation, but right now you do. If you cancel an award stay that has the Hotel portion of a Hotel+Air Travel Package attached, then the greatly reduced number of points for the Hotel portion of a Hotel+Air Travel Package will automatically be returned to your MR account. This is one of many bugs resulting from their October 2007 software downgrade.