I'm boring. My sims usually stay married. I use Wonderful Whims' attraction system so my sims are only allowed to marry sims they find Extremely Attractive as a way to mimic a soul mate situation. Also since Growing Together added compatibility, they have to have at least good compatibility.
With all that being said, my two all-time favorite households have both been married twice.
Orion, the founder of my alien legacy, married Zara Bradford (a sim I made for my save) when a one-night stand turned into Zara getting pregnant. Orion thinking he was doing the right thing, proposed. They had the most toxic marriage I've ever had sims to have. Zara eventually divorced him and left him to raise the twins. He later married Thalia Galanis and they're still together.
My other favorite is my 2nd generation aim in my Westbrook legacy, Emma. She married a sim I found on the gallery. He cheated on her by flirting with the doctor who delivered their son, Elijah. Emma divorced him, and eventually married another sim I got from the Gallery. He was a single dad to two kids. They went on to have twins bringing the total of kids to 5. I haven't played that save in a while but Emma is still one of my favorites.
I'm a hopeless romantic in real life, so I tend to let my sims have their happily ever after.
