Time for points to post + When
 

Does anyone know, how long does it take for US stays to usually post? What time of day do they usually post?

I've had it take up to two weeks, but 3-6 days normal at full-service Marriotts. Will be there by mid-morning if they are going to post that day. Fairfields and Courtyards are usually faster, which I do not understand.

That has been my experience also.
DO NOT throw away your folio until you have seen the proper points post on Marriott.com
As an aside-Just stayed at the Planet Hollywood in LAS.I was SHOCKED to see the points posted on my SPG account when I got home the same night after checking out :D
I never experienced anything like that with Marriott Rewards!

I used to be annoyed by how slowly Starwood points took to post (1-2 days) until I started staying at Marriotts and noticed that it took anywhere from 2-5 days there.

From my experience, 2-6 days for points to post, usually 3-4.

Also assuming days = business days?

I must have been lucky. I am a platinum member, and I can tell you every one of my stays have posted to my account within 48 hours.

William

My experience has typically been that I can see the points increase in my total 2 days after checkout, and then the posting shows up a day later in my account. This is often over a weekend, so it's not just occurring on business days. I do find that certain locations are a bit slower on this, though.

As for holding on to your folio, you can also set up your MR account to automatically email you the bill. I've found that this usually aligns with when the points post, so bill received via email = points posted.