Googled and found this in one of the threads ! Right from the Horse's mouth !!
Q? Will mail sent by BICS to my old address end up at my new address (if I put in a forwarding request to the USPS) or will it end up back at BICS?
Answer Dated: 2003-09-09
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As a Postal Carrier, I can shed a little light. If the mail is NOT indicated with "return service requested" it should be forwarded for 12 months after your move. (Between 12-18 months your mail is returned to sender with your new address--no matter what.)
Since I deal with the BCIS in my personal life, in my duties as a Postal Carrier I tend to take notice when I see letters from BCIS and I have noticed that they are usually not endorsed as "return service requested" so they should be forwarded to you no matter where is the US you move.
I will also point out that in "high turnover" units such as apartments, there may be problems with getting the mail forwarded as sometimes inexperienced carriers may not have time to check all the "forwards" and some items may be delivered as addressed (even though you no longer live there) or returned.
If you think there may be a problem you may want to contact your old PO and have them ask the Carrier at your old address to watch for an "important letter" from the BCIS and be sure it gets forwarded. It may help.
I was lucky, I moved from my old route and know the Carrier who replaced me, so I KNOW she will be sure I get any of my mail that should be forwarded!
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