When did you receive your official acceptance after an unofficial acceptance?

[wwwk454]

Two weeks ago I received an unofficial acceptance email from the program director saying "On behalf of the program faculty, I want to share how delighted we were at your interview and inform you of your acceptance to our program.  In the following weeks you will receive a letter from our admissions department formally informing you of your acceptance to the program and providing instructions regarding next steps."

I know I should be patient since the director mentioned that I will receive my letter in the following "weeks". But I still freak out...! My mind dwells on the worst situation such as the faculty of the department just simply changed their mind. (Because I didn't do well in my interview. I thought I was waitlisted.)
And I heard about sometimes the graduate school of a university rejects someone the specific department recommends for admittance...!

Anyone else in a similar situation? 
How long should I wait until sending a follow-up email? 

[minch05]

Yes, I am in the same situation as you. A professor from the program sent me an email stating that I was recommended me to the grad school and I should expect news in 1-2 weeks. This is almost the 4th week, I still don't have any news yet from the grad school. In the portal, my status is still "Under Grad School Review". It's frustrating. I sent an email to the program coordinator last week and they said dozens of other applicants are in the same stage as me.