So, given the current understanding of the effects of tobacco on human health, it would appear that ‘Longlife’ is not a brand that can suffer the allegation of descriptiveness.
It’s an interesting strategy though (to give credit where it’s due, the brand first arose in the 1950’s when the medical evidence wasn’t around).
The perfect ‘trademarkable’ brand is one that calls to mind the sensibilities you are trying to convey without describing them explicitly.
So, what about a word that describes the opposite? What about a word that describes the opposite and also which is itself laudatory (as opposed to a known ill effect of the product) – as may be the case for this brand of Taiwanese cigarettes? (This latter strategy risks sanctions as being misleading to consumers – though as Danny points out in his post, it may well be the case for Longlife that the truth is so well known that it is not an issue.)
Getting back to a brand that describes the opposite to some characteristic of the product in question – not a bad strategy at all (depending on the context).
Though unintentional, try selling Japan’s famous ‘Calpis’ softdrinks in English speaking countries (they are rebranded as Calpico elsewhere).
Can you think of other examples?