One interesting thing, though not relevant to your long stay, is that Marriott is very inconsistent with its treatment of members vs. airlines directly, in some cases.

For example, Marriott gives Qantas frequent flyers 1500 points per stay, but gives its own members points on a US$ basis. For very short stays, I earn vastly more points by giving them my Qantas card and not telling them I'm in their rewards scheme. Silly, eh?

(Other hotels that I'm aware of don't disadvantage their own members that way.)