"History has an uber-arching theme. When you go there, you have a frame of reference for what you're going into. If you've already bought into 'Hatfields & McCoys,' you're likely to stick around for the next show. . . . That's how you build an audience," Everist said.
History's sister channel Lifetime — both are owned by A&E Television Networks — keeps adding formats to its repertoire, although it's not always clear whether there is an overarching theme. The network runs dramas such as "Army Wives," syndicated series such as "How I Met Your Mother" and reality shows such as "Project Runway."
Rob Sharenow, Lifetime's executive vice president of programming, describes the network's holdings as "a balanced portfolio of investments." He said the advantage of having a varied slate of genres is "in a down market for one genre, you have yourself covered with the other."
Sharenow explained that Lifetime is also hedging its investments by diversifying its formats. Producing a reality show such as "Dance Moms" comes at a fraction of the cost to produce a scripted series such as "Army Wives."
A scripted series can pencil in at $1 million per episode, whereas reality shows come at 10 to 20 percent of that cost, estimates Williamson, of Central Michigan. Cable networks are taking that expense into consideration as they wade into dramas and sitcoms.
Bravo, for its part, is starting out with two scripted shows due out next year. The network that built the "Housewives" franchise is sticking to its lifestyles-of-the-rich-and-naughty theme. One show, "22 Birthdays," follows wealthy families as they throw lavish parties, while "Blowing Sunshine" looks at the interactions of staff members and patients at a private rehab center.