"I give it 12 months," we say, while sitting in a dusty church pew wearing our oversized hat or only clean suit.
"Oh, I don't know. She's a bit friendly with the best man, if you ask me. Six months at best," someone will mutter, just before singing a love song specially chosen by the newlyweds.
We fancy ourselves as knowing just how long it will take before a happy couple becomes an it's-your-fault-you-lazy-faithless-farm-animal couple. We'd put money on it.
So sing hosannas to a disruptive tyke of an iOS app called ForeverNOT. This entirely helpful social service allows you not only to bet on the potential length of your own friend's relationships, but also those of famously true lovers.
Yes, like Kanye and Kimmy. And Jennifer Aniston and whatshisname.
We feel like we know these people, even if we're then surprised ourselves when we discover they're not quite what was projected by their fine publicists.
There is, though, an aspect of this free app that is bracing in the extreme.
You know how you just don't have the courage to tell your BFF she's marrying a man whose wit glass isn't even half full? Well, ForeverNOT allows the happy couple to see what you really think.
However, with the beauty that is currently very popular in apps, they won't know who said it.
You, therefore, can be sanctimoniously secure that your opinions are being registered by those at whom they're directed.
And the cheery coupling? Why, they'll have hours and hours of fun (with their shrink) pondering not only that their friends think they have a 15 percent chance of surviving till Christmas, but that these supposed loved ones are too gutless to tell them the truth.
It's so post-post modern as to be, well, modern.