DDB recently celebrated a special birthday – it is 20 years since the Felix cat food TV campaign first appeared on UK TV. Since then, it has run consistently across the UK and Europe, with hundreds of executions, across multiple media, launching new products and with the famous black and white cat appearing on everything from posters to tea-towels.

Felix has only ever had one campaign. Few campaigns anywhere in the world have run continuously for so long. Like the advertising jingle, the long-running campaign now seems an anachronism. This is bizarre, really, since client briefs rarely ask for campaign ideas that will need changing quite soon.

So why are long-running campaigns becoming an endangered species? On the surface, it seems to result from managers acting responsibly – a result of wanting to keep brands fresh and avoid ‘wear-out’. Indeed, the ‘disruption’ orthodoxy claims that brands need to be in a state of ‘continuous revolution’ to survive.

But, in reality, the desire for change usually has more to do with marketing and advertising egos than responsible brand stewardship. It has long been a truism that marketing and agency people get fed up with campaigns long before real people do. Changing the campaign is a quick and easy way for managers – client or agency side – to make their mark. ‘Brand X stays with long-running campaign’ is never going to make the front page news. One of the hardest marketing skills to master is the art of leaving well alone.

But does all this chopping and changing do any harm? We believe it does. No-one is arguing for the continuation of ineffective campaigns, or for running the same execution for years. But there is evidence to suggest that, once a winning formula is found, advertisers would be well advised to stick with it.

Campaigns, even individual executions, take much longer to wear out than is often feared. Having studied decades of econometric analysis on the subject, one major advertiser recently concluded the idea of wear-out may be a myth.

Recent thinking on how advertising works points to the importance of continuity and consistency, rather than disruption. It is becoming clear that the old persuasion model is flawed. Most effective advertising works by building emotive associations at a less conscious level. This takes time and, above all, consistency, so new communication builds on what has gone before.

As a result, the relentless pursuit of novelty can lead to money being wasted. Advertisers spend precious management time developing new ideas, and ROIs fall as people encounter a flurry of inconsistent campaigns. Our econometric work on Felix showed the advertising becoming more, not less, effective over time. That's the virtue of consistency.

The design industry seems to understand this better than we do. The Museum of Brands, Packaging and Advertising in London shows the careful evolution of successive pack designs for great brands like Hovis, Persil and Heinz over 100 or more years – each new design subtly building on the last, always balancing consistency with the need for design refreshment.

There are sound neuroscientific reasons for this sensitive approach. Brands can be thought of as well-trodden paths of neural connections that help us to make buying decisions more efficiently, with minimal mental effort. We disrupt these associations at our peril, as the recent Tropicana US pack redesign showed. When long-standing elements of the pack design were changed, sales fell alarmingly as people found it harder to spot Tropicana on the shelf. A design volte face swiftly ensued.

We all spend a lot of time thinking about the relationship of ‘consumers’ with the brands they choose. We spend far less time thinking about our own relationship with the brands we are responsible for. The best brand custodians are much like the best parents – they know the value of consistency. As Jeremy Bullmore once said: “What most successful brands need is constant and affectionate maintenance.” There is no room here for career-boosting ego trips masquerading as sound marketing practice.

This article originally appeared in the July/August 2011 issue of Admap. Click here for subscription information.