I-94 aka Arrival Departure Record is what governs your status in the USA. An expired I-94 can lead to bar from entering USA for 3 to 10 years.See details on "Unlawful Presence".
Time taken for a check to be valid after the time of arrival at the USCIS - The USCIS usually processes the fee-ing in of most of the applications within 24 hours of receipt. The bank has the option to accept or reject a fee instrument that expired at the time of its deposit. If the bank for expiry rejects the fee instrument, then the bounced check procedure is implemented and pursuant to 8 CFR 103.2(a)(7) (ii), the finance center will issue a bounced check notification.
I had a question about the H4 extension for my daughters.
My H1B visa is stamped until 10/05/2009 for my earlier employer A,when my current employer B transferred my H1B the new NOA had a validity date of May 2010.
My daughters have a valid H4 visa until May 2010
When I returned back from a visit to India back to the US the official at the Port of entry stamped our I-94 until the expiry of the H1B visa for Emp A for oct '2009 for the whole family.