And 2004 looks unlikely to be any different, with the first new product of the year hitting US shelves and cooler cabinets this week. Diet Coke with Lime is being rolled out throughout the US - with the rest of the world to follow later - and follows earlier cherry, lemon and vanilla variants of the iconic cola brand.
"Consumer research indicated a preference for lime as the next Diet Coke flavour, as it's a flavour combination many people already are enjoying," said Ed Klein, vice president for Diet Coke at Coca-Cola North America.
"The natural citrus taste of Diet Coke with Lime received extremely positive feedback in consumer testing."
As is usual, advertising support for the launch will be significant, with national radio, print, out-of-home and Internet components. The packaging for the new soft drink maintains the classic Diet Coke look but is also noticeably 'lime', with a distinctive green swirl underlining the Coke name.
Diet Coke with Lime will be offered initially in 20-ounce and 2-litre bottles, multi-pack cans and 8-ounce bottles.
The positive consumer reaction to the new flavour and the drink's formulation has prompted Coca-Cola to rethink its Diet Coke with Lemon brand as well, the company said.
"Because of the positive response to the light, natural citrus flavour of Diet Coke with Lime, the same flavour approach is being applied to a reformulation of Diet Coke with Lemon, which will have a lemon taste that is lighter than the original version. New packaging graphics for Diet Coke with Lemon also will harmonise with Diet Coke with Lime.".
Since its launch in 1982, Diet Coke has become the number one diet soft drink in the country and the world, and the third best-selling carbonated soft drink overall in the US and the world , the company said.
The company has not yet said when (and indeed if) the new Diet Coke variant will be launched in Europe, but the likelihood is that it will follow a similar pattern to the vanilla and lemon variants and be introduced in selected markets over a period of months.
The big question now is whether arch rival Pepsi will follow suit - as it has done with most of the other flavour variants - and launch its own lime-flavoured soft drink.