When does a brand become a piece of Americana?

In marketing strategy courses throughout the country students learn the importance of managing a brand or product by its stage in the product life-cycle. It is drilled into their heads that every product will inexorably move through each stage of the cycle until it is ultimately cast into the dustbin of irrelevancy. They learn that investing heavily in advertising and promotion in a product's introductory and growth stages is an important determinant in whether the new product will get off the ground. They also learn that cutting back ad spend as the product progresses on through maturity and eventual decline is often just as important. But what they don't learn -- perhaps because it countervails existing dogma or simply because it is seen as anomalous -- is that some brands are so indelibly linked to our unique American consciousness that their absence from the marketplace is near unfathomable. 

In fact, we recently came across such a phenomena with a client in whose portfolio resides a brand so iconic that it is difficult to imagine a world in which it does not exist. This raises a variety of questions: Do iconic brands prevail simply because they have stood the test of time? In other words is it inertia that keeps these brands alive? And if so, how immune to the product life-cycle are they? (And perhaps more importantly, how do I get a job as one of these tried and true products brand manager?) Jocularity aside, what does it take to create a brand so strong that it becomes inextricably linked to our collective consciousness? We know there is such a thing as 'too big' to fail. Is there such a thing as too old to fail? And if so, what does that mean for the organizations that own these brands? What responsibility does that thrust upon them?

We spent many a night pondering such imponderables (and came up with largely nothing to show for it) and now we would like to pass them on to you. So in a nutshell: what does it take for a brand to become a piece of Americana?