After a half-hour wait the checker rings up your purchases. There's been a mistake. One of the primary functions of government is to protect a minority from the excesses of a majority. For example, consumers are protected from being defrauded by large corporations by many laws that regulate how those companies do business. Unfortunately, laws are slippery things, and there are many legal loopholes through which companies can get away with murder.
Rebates are a loophole big enough for the space shuttle.
Recently I heard a radio talk show on consumer issues. They also have different requirements. And all of them say you should expect to receive your rebate within 6-8 weeks or longer. Companies make the rebate redemption process complicated on purpose. I sent in everything as requested and heard nothing.