Just read an interesting paper from Decode Marketing, which gives some real scientific under-pinning to the concept of "fresh consistency".
The Decode paper reports on scientific research into the way our brains process information, done by Radboud University in the Netherlands. This shows that too much consistency is ineffective. If a stimulus received by the brain sets up an expectation which is then confirmed by a subsequent signal, then the reaction of brain cells is reduced. For example, you're watching a TV ad, you say to yourself, "This looks like another ad from brand x", and as you watch you see it is indeed what you were expecting, your brain switches off to focus on other stuff.
You can see this on these scans of brain activity done by the researchers. On the left, is what happens with an expected signal, and on the right the higher level of activity from unexpected stimulus.
... but too much freshness is also bad
On the other hand, too much freshness is also ineffective. 'Disruptive' communication that is completely unexpected does grab attention and get your brain working. But this is hard to keep up and needs a high level of involvement. And most advertising tends to be processed with low involvement. To quote a Milward Brown paper from WARC, "Sadly for advertisers, brands and advertising are not particularly important to people. We usually watch TV to be entertained rather than to actively “learn” about brands, so the chance of remembering ads is generally low.'
Therefore, the optimum approach is based on the 'MAYA' Principle: Most Advanced, Yet Acceptable. Many studies have shown that a message that is moderately in line with expectations is the most efficient at increasing: (a) Attention, (b) Liking and (c) Recall and Recognition. In other words, what we are after is fresh consistency. On the one hand, we need consistent elements, in terms of brand story and brand properties. But we also need to keep the brand fresh.
For example, in a post here on how Sainsbury's I looked at how the retailer had used chef Jamie Oliver as a spokesperson to bring to life the "Try Something New Today" brand idea. Fresh consistency was created over 11 years and an amazing 100 commercials, with the freshness coming from a stream of service and product innovations.