I cannot speak to Mississippi checks. My understanding is that they have to adhere to the UCC, unless there is an agreement between the parties to the contrary. The timing constraints will depend upon what is forged -- the signature or an endorsement.
U.S. Treasury checks are subject to much longer return schedules. In general, a bank could be hit with a claim as long as 18 months after the issue date. For details, look at 31 CFR Part 240
, particularly at §240.8.