This is what passes for a revolutionary approach in radio: A rock station in Sydney has drawn worldwide attention for its promise never to play more than two commercials in a row. A locally owned country station in Lisbon, N.D., made a similar pledge a few weeks ago.

Result: The Sydney station rocketed to the top of the ratings and the North Dakota station won immediate and strong praise from listeners.

But in most of the radio industry, such breaks from the rule of 8-, 10- and even 15- minute marathons of commercials are viewed as an aberration.

Defenders of the standard American "stop set" -- the industry term for what happens when the music stops and a station plays one ad after another -- say only stations facing little competition can afford to cut down on their commercial load. Most stations go up against competition in which the other guy offers advertisers discounted rates, which means you have to lower your price for air time, which in turn requires you to sell more time to make the same money -- thus, ad clutter.

Not very long ago, the standard radio ad break was perhaps 90 seconds or two minutes. But the meaning of "We'll be right back" has changed dramatically in recent years. Federal regulators once set a cap of 18 minutes of commercials per hour, but all government guidelines governing programming were erased in the 1981 deregulation of radio. Now some FM stations' ad packs are approaching the interminable -- up to the 15-minute breaks heard on talk shows such as Howard Stern's morning raunchfest. Ad breaks on the Stern show have been clocked at as long as 18 minutes 48 seconds, with as many as 30 separate spots jammed up against one another.

With commercial loads of 25 minutes per hour increasingly common on the radio, does anyone stick around until the next segment of the program?

Stations sell time to advertisers based on research showing that the fewer times programs break for commercials each hour, the happier and more loyal listeners will be. Thus evolved the two-per-hour, but hugely long, stop set.

Perturbed by this trend, stock analysts last month predicted slower growth for six major radio companies, and investment banks downgraded their recommendations on those companies' stocks.

And recent studies show that a chief reason for radio's declining audience is the complaint that the ads go on forever. In a study by Paragon Media Strategies, 70 percent of listeners said that because of ad clutter, they now spend more time flipping through stations than they used to. From 1999 to last year, the percentage of listeners who punch up another station as soon as they hear the first spot jumped from 6 to 13.

But conversely, in the same study, only 25 percent of listeners said they'd prefer more breaks with fewer spots over longer breaks that permit stations to play longer sets of music.

What should stations do? The trade magazine Radio World recently urged stations to reinvent how they present commercials, with fewer and shorter spots that might well prove more effective for advertisers, who aren't exactly thrilled about having their message run as No. 17 in a clump of 25 consecutive ads.

As for listeners, they continue to flee to Internet radio and satellite radio, both of which are largely commercial-free.

Listeners to the FM talk shows like that of Howard Stern, above, often hear "stop sets" or "ad packs" that last for 15 minutes or more.