Another reason why open relationships don't work in practice for a lot of women is because they're simply too time-consuming. Block is up front about the work involved in juggling a husband and a girlfriend. An excerpt of her book on Huffingtonpost.com, "Life In An Open Marriage: The Four (Not-So-Easy) Steps" (also excerpted on YourTango), prompted one HuffPo commenter to say, "I'm exhausted just reading about all the 'work' and never-ending 'communication' about feelings, situations, jealousy, worry, etc. It all sounds like much more effort than its worth (IMO)." Likewise, Taormino's Opening Up: A Guide to Creating and Sustaining Open Relationships is an intimidating 300 pages, in which the kind of person who is successful at non-monogamy is described as someone committed to knowing themselves "on a deep level," a process she says might include "psychotherapy and counseling, reading, writing, journaling, blogging, attending workshops and peer support groups, meditation, and various spiritual practices." While the idea of openness may be appealing to some women, it's hard to imagine many of us finding the time to juggle a second relationship. Especially those of us with careers and children.

Open relationships are being billed as the wave of the future, but they’ve actually gone in and out of style every few decades, never becoming more than a fringe movement. According to Susan Squire, author of I Don’t: A Contrarian History of Marriage, "there have been experiments of mate-swapping in the 19th century and again in the 70s and in a few Utopian societies, but it never seems to stick. It doesn't work or only works for a short period of time. Then, history cycles, marriage cycles, and everything repeats itself."  The last time open marriages (often known as polyandry, free love, friends with benefits, et al) were in vogue was during the sexual revolution of the late sixties and seventies. In 1972, the landmark book Open Marriage, documented Nena and George O'Neill’s attempts to redefine marriage and open up their relationship to other partners. It was a runaway bestseller and, like today, promoted the impression that open marriages were the way of the future. By 1977, Nena O’Neill had published The Marriage Premise, which argued that fidelity was not such a bad thing after all. Squire herself got caught up in what she calls "the five minutes of open relationships" in the seventies. In her first marriage, she says, "we did this thing where we had to tell each other but we could f**k whoever we wanted. Did it work? No. I remember him calling me to tell me he was drinking with some woman, and saying 'I'm going to go sleep with some woman, do you mind?' Of course I minded. When faced with that, I wasn't into it. And the reverse was true as well."