Oath notice expected time

Proxyon

Registered Users (C)
I passed successfuly the whole naturalization procedure and the interview. My oath was scheduled for July 25, 2012, but I failed to go to the ceremony, because of health problems. I went to the local USCIS office in Massachusetts and asked them for a reschedule date in October. They said I will be fine, the only thing I did was I wrote down on a small paper list the month when I'd like the oath. They said I will be notified via regular mail exactly when and where the oath will take place.
My question is this:
How long before the oath date does the oath letter arrive ? I know it depends from state to state, but may be some of you know some average time ? I am out of the US right now and want to sharpen my roommates' attention regarding the expected date of the notice arrival.
 
Thanks for the reply and the website given.

What I see there scares me a little. I don't know how certain is that information, but I've seen cases where the letter is received and the oath is after two days. Wowww ! If that happens in my case (I hope it won't), I wouldn't have enough time to buy a plane ticket and go to the US for the oath.
The other bad thing is the calling USCIS doesn't work, cause they don't know what is going on in the local USCIS offices. And the local USCIS offices who are responsible for scheduling oaths do not have a customer service phone, where you can call and ask questions about your case.
 
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