By Lynn Beresford

Anyone who can still sing the "I wish I were an Oscar Meyer Weiner" song knows ad campaigns can stick with you for a long time. In fact, according to a recent study conducted at Ohio State University in Columbus, advertising typically affects purchases for six to nine months--catchy, effective advertising, that is.

Determining your advertising's longevity can help you plan better timing and placement for your ads, says Robert Leone, the study's author. For instance, if you determine that your print ads are remembered for four months, you probably don't need to run them in a weekly publication; instead, space them farther apart.

Television, radio, magazines, newspapers . . . is one medium better than another for helping customers remember your product? According to Leone, how well and how long people remember your ads has more to do with the ad's cleverness. Also, remember that promotional ads--such as coupons and special discounts--usually enjoy less longevity since they're intended to get consumers to act immediately.