A lot of the argument against Brett Favre coming back is that he might somehow "taint his legacy" by doing so.
For all that sportswriters love to trot the same tired examples out, our enduring memory of Willie Mays involves Vic Wertz, not a Mets uniform. With Montana it has nothing to do with the Chiefs; with Steve Carlton nobody thinks of him as a Twin. "Legacy" is forged long before an athlete gets to try to "hang on too long", and it is cast and cooled in the minds and memories of fans. No matter how many past-their-prime games these guys play in, it is their primes that we will in fact remember, and cherish, and reminisce over.
The real issue is whether the Packers should hold their season hostage to a guy who, even now, can't say with 100% certainty that he wants to come back and play. And that's a business and professional decision, one that legacy does not and will not enter into.