Read this column from the BusinessMirror, regarding the seven-day exchange policy of some stores. It turns out, you can actually return defective items even after that period, especially for products bought from well known brands. (Of course, if you buy a defective item that was just smuggled, you have no avenue for redress.) So if I were you, if you buy especially big-ticket items like appliances or even a pair of shoes or bag, make sure you keep the receipt.
It is important to note that in case of hidden defects, the law prescribes a maximum of two years from the date of purchase or upon discovery of hidden defect to file a complaint or act, taking into consideration the nature of product purchased. (Click The Business of Consumers for the rest.)
Unfortunately the column doesn't say what happens if you don't have the receipt for the product purchased anymore, and what if the store doesn't want to exchange the item you bought? I've already experienced complaining to DTI's consumer action group regarding some defective product purchased but received no support from the agency at all, other than a letter stating that they forwarded the matter to the agency overseeing the product/brand. So there.