Thanks to the safer world in which we live, life expectancy keeps climbing. Once the world goes Kurzweil, who knows how long we'll hang around.
This spike in life expectancy doesn't bode well for the already stooped, arthritic, and tremoring institution of marriage. In the old days, loving someone forever meant loving him/her until about 65. Now you have to limp through it until at least 85. It's true that people aren't getting married as young, but getting married at 32 instead of 24 still means today's married folk have to tolerate their "soulmate" for 12, 13, 14, 15 extra years to make it to "forever." Not strangling someone for 40 years is a lot easier than keeping your hands off their throat for 55.
Modern medicine has also greatly improved quality of life. Today a man of 55 can physically er, perform in ways he couldn't a generation ago, and thanks to the ubiquity of divorce, he now has a deep talent pool of divorcees to target. When you're a vigorous 55 and can pull a 40-year-old eager to have someone lie to her about how beautiful she still is, that "forever" vow you made to your now musty 55-year-old bride feels like a belly flop into the River Styx.
A lot of women talk about liking older men. That's acceptable when you're 28 and he's 40. But what happens when you're 53 and he's 65. Suddenly the allure of an older man isn't so alluring, particularly when you know you're going to be watching him decay for a couple more decades. Forever suddenly feels like the kind of forever you complain about at the DMV.
Thanks to dating sites and Facebook, it's never been easier to meet someone new. A 55-year-old divorced person can hop back in the game with a few mouse clicks; no embarrassing 50+ dance nights at your local community center. You can point and click at a wide range of partners your age and start the second (or third or fourth or fifth) stage of your romantic life.
The power of that very media is another marriage killer. There are now so many forms of communication; texts, email, constant cell phone access, which means non-stop opportunity for marital misunderstandings, words said in heat, and just plain overexposure to your now never disconnected lover. Everyone is just one unfortunate auto-complete away from relationship oblivion.
Medicine is only getting better, and technology is putting us in touch with ever more people (potential sex partners). None but a very select few can tolerate a sixty-year marriage. Given that the only people who left who take their religion seriously are Mormons and Muslims, the "forever" marriage vow will soon make even priests laugh out loud. In the future, the only way a couple will be able to last until death do us part is to hire a hitman (probably through social media).