Advertising has probably been around for as long as there have been merchants with goods to sell. In the ruins of Pompeii, archaeologists found advertisements for various wares engraved into the walls of the city; however, it was with the advent of printing that advertising really took off. By the 17th century advertisements were a regular part of the English newspaper. The demand for advertising grew as the economies of the United States and United Kingdom did. It was for that reason that in 1843 the first advertising agency, Volney Palmer, was opened in Philadelphia. Naturally, among the advertising agencies' tools is the advertising slogan.
An advertising slogan is simply a short slogan which is meant to promote a product. Ideally, an advertising slogan should help the consumer remember the product, not to mention distiguish the product from other similar products (say, Coke from Pepsi for instance). It must be noted that the best advertising slogans usually bring to mind the brand they are promoting any time that they are mentioned. "Fly the friendly skies" immediately brings to mind United Airlines. "The King of Beers" brings to mind Budweiser.
Of course, while advertising slogans are meant to be memorable, some are more memorable than others. I sometimes believe that Coca-Cola has been responsible for more memorable advertising slogans than any other company. One of its most famous slogans was "The pause that refreshes," coined in 1929. The slogan may have taken its inspiration from an earlier 1924 slogan, "Pause and refresh yourself." Coca-Cola's other famous slogan, "The Real Thing," from 1970, also had its roots in an earlier slogan. In that case, it was "It's the real thing" from 1943.
Of course, Coca-Cola is not the only carbonated soft drink to have catchy slogans. Seven-Up has been the Uncola since 1967. A & W Root Beer has been "that frosty mug sensation" for many years now. Curiously, it seems to me that Coke's rival, Pepsi, has always had a problem developing memorable slogans. The only one I can remember is "the Pepsi Generation," a slogan they adopted in 1964, and I think that is only because they insisted on repeating it in one form or another for literally years.
The best advertising slogans do last literally for years. The New York Times has touted that it has "all the news that's fit to print" since 1896. Morton Salt has used the slogan "When it rains, it pours" since 1911. Maxwell House Coffee has been "good to the last drop" since 1915. FTD has been encouraging people to "Say it with flowers" since 1917. And Wheaties has been "the breakfast of champions" since the Thirties.
Even when a company stops using a particular slogan, it may well persist in the public's minds. Kentucky Fried Chicken touted itself as "Finger lickin' good" beginning in 1952, yet, while they long ago abandoned that slogan, it is the one that people tend to think of when they about Kentucky Fried Chicken. For all that M&Ms might proclaim that "Chocolate tastes better in colour," most people probably think of the slogan "M&Ms melt in your mouth, not in your hand (started all the way back in 1954)" when they think of the brand. General Electric abandoned the slogan "G.E. We bring good things to life!" in 2002, but more people probably associate it with the company than other slogans.
It also seems to me that often a company is lucky to get one classic slogan (Coke must be very lucky). In 1971 the classic slogan "You deserve a break today" was used to promote McDonalds. To this day, people still associate it with the brand. And yet the past few years have seen a succession of, in my humble opinion, some rather lame slogans used to promote McDonalds: "We love to see you smile," "Smile," and, worst yet, "I'm Lovin' It." One thing I can say about Burger King; they have never wholly given up on the classic "Have it your way..."
I have often pondered why companies sometimes change their advertising slogans. I would suppose it is to keep up with the changing times, to give the appearance they are still "hip (I don't even know if it is hip to say "hip" anymore...)." As I see it, however, it might be best to simply find a good slogan that the public remembers and stick with it. Everyone thinks of Wheaties when they hear "the Breakfast of Champions." "Leave the driving to us" brings to mind Greyhound Bus Lines. Can anyone tell me the product that was promoted with the words "Generation Next?" That was Pepsi Cola's slogan from 1997. I doubt anyone will remember that slogan 60 years from now...