I spent 4.5 months at a Residence Inn about 5 years ago, waiting for a new house to be finished.
First of all it was a great experience! 4 of us and our dog in a 1 bedroom, 1.5 bath suite, but we never felt crowded. The staff was great, and really understood the needs of long term guests.
Daily maid service was really nice, especially since they cleaned the pots and pans from any cooking we did.

As for points, I since I was paying for it myself, I used my personal credit card, so I got all the points. I am not sure, but I would guess that paying the bill yourself and getting your company to re-imburse is the sure way to make sure. But you could call Marriott Rewards to check.

As VA1379 mentioned, it is only 5 points per dollar, but it really added up in both points and status.

Have fun!