Here is a Politico article on the age of Fox News viewership. For O'Reilly (their most "influential" host) it's 72. For the whole thing, it's 69. In 10 years, the entire viewership will have literally passed away...
https://www.politico.com/blogs/media/2014/05/may-cable-news-ratings-spare-no-one-189393.html
Edit: BTW, to put the number of viewers into perspective, 25m people watched the the NBA finals per game. A show I've never heard of called What Would you Do pulls 10 times the viewing numbers of Fox News most viewed programs.
https://www.politico.com/blogs/media/2014/05/may-cable-news-ratings-spare-no-one-189393.html
Edit: BTW, to put the number of viewers into perspective, 25m people watched the the NBA finals per game. A show I've never heard of called What Would you Do pulls 10 times the viewing numbers of Fox News most viewed programs.