1 a: a story coming down from the past; especially : one popularly regarded as historical although not verifiable
That's how Webster's online dictionary describes the word. Still nothing definitive about time, so that is apparently subject to some further interpretation. I find it difficult to apply the term legend to someone who still has a significant degree of their life ahead of them and so recently retired sports figures, 50-something rock and rollers, politicians and business people don't really rate the term in my mind. They might some day, but don't you find the media and marketing types far too quick to call all sorts of questionable events and products legendary?
I suppose that the fact that Webster's suggests that the idea of a legend is unverifiable would lend some credence and justification to the word's use. They do use the word "historical" in their definition however and so that may hold some sort of key to solving my dilemma.
1 a: of, relating to, or having the character of history
So, even Webster's can't provide a specific amount of time to determine something that is historical and by extension, this would apply to the word legend. However, they do offer a strong hint with the use of the phrase "in the past" and for me, that confirms the need for the whole affair to be something that is finished in some way. All of this verbiage to tell you that the word "legend" is vastly overused in our world of hype and hyperbole and a great case in point is the commercial that inspired this particular writing. In response to the claim that the McRib sandwich is "legendary," I can only say that it is, at the very least, unverifiable.
Now, if we wanted to talk about some of my historical St. Patrick's Day exploits, the ones that I still don't want my kids to know about - now they would be "legendary."