I have had to fax in 4 missing stay requests this year and 3 last year.
The hotels I have had problems with vary from Marriott resorts to Fairfield Inns to Courtyards--there seems to be no set pattern except that the Marriott corporation is not doing a good job at keeping up with it's rewards program. I usually wait 12-15 business days before faxing in the missing stay request. I have also had to fax the request in 2-3 times on two occasions. I would give them a week, then fax it again again and mention on the fax that this is the second request.
I can't explain it, but I have watched it closely to insure the proper points are posted.
I enjoy staying at Marriott's, but this is an area of service that they could improve on.