I think longevity does have to be taken into account.

Sinister...what do you mean 14th? Currently? Last year was the best year of his career...stats wise.

Favre is 40, Staubach played until he was 37, Unitas played until he was 40 but only played one full season in his final 6 seasons.

Montana played until 38 and only played in 26 games his last 4 years.

Bart Starr played until 37, but his last productive year was at age 34.

I don't know what you are getting at with your statement. It seems like you, either don't know the stats or are comparing these other guys' primes to the end of Favre's career.

BTW...Favre is 10th among active QBs is passer rating at 86.3.
http://www.pro-football-reference.com/leaders/pass_rating_active.htm