The first time I gave them 60 days from the date I expected them to receive it. And actually they mailed it within about 6 weeks. But as I said, I never received it because it was sent via USPS First Class. Since I have a mail slot on my front door, I can only suppose that 1) the post office lost it, or 2) a postal worker stole it for the personal information contained. I've been monitoring my credit ever since.
I have spoken with the FBI about my case several times in order to get as much information as possible. What I learned was that they need at least 2 weeks to process a fingerprint card from start to finish. But that's only after they "begin." It may take them a week or more after they receive it before they begin processing it. So if you put a "due by" date on the outside of the envelope and on the application, they will open and begin processing your application sooner.
Second, if you want to have it returned faster, you must pre-pay with some sort of courier envelope - you can't use your credit card. For instance, you could use a FedEx air waybill, but you would need to use a FedEx account to bill it to. You couldn't just write your credit card number on the air waybill (I tried). Even though FedEx would accept that, the FBI won't. So along those lines, the cheapest way to get it back quickly (with no problems) is to enclose a USPS Express Mail envelope and then enclose enough postage (stamps) to send the envelope with about 8oz. of mail. It will likely be lighter than that, but you should send too much postage rather than not enough.
If you don't put the dates on the envelope and the application, your background check could take up to 3 months. Since all we have is 90 days from the tentative approval date of the permanent resident visa, you should definitely put the date on the FBI request.
