Dumper says the willingness of the agency to innovate over the years has played a big role in ensuring the longevity of the partnership.
This award is particularly significant in that partnerships between marketing departments and their agencies have been undermined in recent years by the declining tenure of chief marketing officers in a single company.
A 2016 UK study found that the average tenure of a chief marketing officer has dropped to around 18 months.
As marketing departments change, agencies often end up becoming a casualty as new marketing bosses look to change things up.
Another by-product of these shorter tenures is that marketers look for short-term gains, rather than longer-term brand building.
On a recent visit to New Zealand, researcher Peter Field noted that this short-termism was hurting businesses.
He said that if businesses just focus on short-term marketing results, this will eventually undermine the strength of the brand in the long run.
He said strong branding had become particularly important in the increasingly digital media landscape.
"The world in which brands are now competing with each other in the digital sense is viciously crowded and wildly competitive," he said in an interview with the Herald.
"And in that kind of environment, if you haven't got a powerful brand, you are stuffed."