I'm getting on up there in years and I can tell you that this is one of those conversations every couple needs to have before they get married. One of the comments here is that it has been working flawlessly for thousands of years. That is not entirely true. It usually Does work for them in the short term, but it also usually wrecks a marriage in the long run. Here's the thing, if a couple freely give themselves to each other in those early years it is one of the things that make it possible for people to still "want" each other even after they are old, wrinkly, saggy, and smelly. By using sex as a weapon they are killing any love that might be in their marriage.