In media bigger is usually better. Large posters are better than small posters. The Cinema works harder than TV. And longer TV commercials are better than short ones.
Several clients have asked me if we had any research to prove that shorter commercials are just as effective as longer ones. We do but we've hidden it.
That's a joke
As with everything in media if you are not sure - copy Procter & Gamble. They buy the cheapest airtime, on the cheapest channels in the cheapest dayparts. But they use long commercials. They probably know something
60 seconds commercials give greater ownership of the break, offer greater viewer involvement & are more confident. Witness the recent Hovis epic. It was 2 minutes long. Or the T Mobile Dance, again 2+ minutes. Save money on expensive channels, dayparts & programmes & splurge the cash on lovely long commercials