People love to swear too much. Its not only lost its flair, but it is also becoming quite annoying, and it can make someone look like a complete dumb fuck (yeah, I know) if used as a comma, which lately, it has been. Since there are traffic lights right outside my apartment, and I live in the city, I get treated to hearing "You fucking fuck! What the fuck? Fuck your shit! Move you fuck!" all day and all night.
So, to answer the question on age limits of swearing, what age would it be where someone learns, not only how to swear properly, but to be able to do so without sounding like the Smurfs as directed by Tarintino.