I'll add to the folio issue. I just did 10 months of expense reports totalling 22k (I'm an idiot, I know but when you work with other peoples money all day long - yours tend to suffer).

I discovered that TWICE that I had checked out of a Marriott FS hotel a day early than reserved and gotten a final folio. My card was charged 5 nights instead of 4 and in one case even charged the wired for business (WFB) rate for the night. And the email folio reflected the extra night too.

A saving grace is that even 8 months later, a phone call to Marriott Business Services and 20 minutes later, credits were promised without too much arguement.

I heavily audited the rest of my 80 nights and only found charges for a few WFB nights that I know I did not use but its not worth the hassle.