I agree with whomever said to make photocopies of all your rebates. Including UPC, receipts, completed rebate forms, etc. Keep a folder of all your rebates and date them, date sent, and expected date. This makes the whole process a lot easier to keep up with.
They are banking on you forgetting or giving up on the rebates. I read somewhere that for ever $100 rebate a company offers, their actual expense is $20. :Q