Reach and frequency are additional factors that affect the duration of a campaign. Reach is the number of people who see an advertisement. Frequency is the number of times the same person encounters the ad. Higher frequency usually leads to a shorter duration. Low reach may be associated with a longer duration. A typical advertising campaign lasts one to two months to optimize reach and frequency. (See FREQUENCY and REACH for additional information.)
When an advertised brand has generated an impact on consumers that is strong enough that the brand is remembered when the time comes to make a purchase, carryover effects are present. Durable
goods such as refrigerators and televisions are purchased only when the need arises. The time between purchases is often years. Therefore, consumer decisions to buy such products will occur at any time. Advertisers of these types of products advertise continually in order to make sure consumers will either see ads just when they are in the market for the product or remember the company and the product due to the presence of carryover effects.