I was wondering, why do beards keep growing and not stay at the optimum length.
Or,... put another way,...
think of your a stereotypical 'prehistoric man'.
http://www.stayfitbug.com/wp-content/uploads/2010/09/cavemen-food-nutrition.jpg
Has he long hair?,.... probably.
Has he a long Gandalf style beard? NOPE!!!
And why not,... we can't assume prehistoric man cut his own hair on his chin, but not on his head.
SO why is he always depicted with long hair and ONLY heavy stubble and not a crazy long beard.
If this is the state us men would get in without the occasional trim, why stop the length on prehistoric man?