Women are machines with three buttons you can press, press them enough and in the right order (but not so much that they take it for granted) and she will remain something that resembles happy

Sadly despite their 3 'women' buttons they also a fourth button that meddles with these first three and can inhibit their effectivness.

First three buttons are: Financial (resource based) Emotional Sexual

In that order. What I mean by buttons are that these are the three elements of her life that when provided it will make her evolutionary triggers in her brains light up like a christmas tree, pump her brain with happy chemicals, and she will be happy as a clam. Women want financial security and the assurance that they have a source of resources. They want the seratonin hits that come along with an emotional pair bonding to a mate (they also get this from having kids) And lastly they want that occasional 'hit' that comes from sexual activity. Infidelity comes generally from not meeting one of these needs, but can also come from the magical 4th button. This is something all humans have built in, but its the desire to have what one 'doesnt have'. So if you are rich, know how to make your partner cum, and provide her with enough emotional stimulation, all the while making her work for it: you get a happy women who won't leave you.

Minimize her desire for what others have, by limiting how often you give her any of these three stimuli. Make sure you also make her work for them, or else the female loses interest and starts fantasizing about what other have or what she thinks others have. Women are jealous creatures by nature, trained to look to what they view as the 'alpha females" in their populations, and allign their desires with what that female has. Media tweaks that last one alot. So talk to your partner backhandedly about how unrealistic those shows/magazines are. Emphasize how miserable other people are etc. Do whatever you can to derail her fantasies in this respect, but don't make it seem like you are crushing her fantasies.. or she will resent you. Hence me advising you to proceed in a backhanded way.

It is also wise to hedge your own bets by having a private detective trail your wife if you suspect infidelity, and keep a mistress on the side (young and attractive) so if your wife does throw a curveball at you, you won't feel too bad as you have been nailing a younger more attractive women the whole time. Don't disclose this to anyone though.

And final thought.. pre-nup

-yes i am in a relationship, and I have never been divorced... and I am not a women hater.. just a scientist with a very reductionist perspective of human motivation