I have consistently put my shelf life for romantic relationships at 5 years. Someone needs decent frame to get 5 good years. Frame issues are known to reduce that number.
I am aligned with the two of you on this idea.
One thing that I think is problematic for a lot of people is that it is common for romantic relationships to go longer than 5 years. In my social circle (some of which is discussed in the thread below), I know many couples that have been together longer than 5 years. Many of them have been married longer than 5 years now and have relationships that have been 7+ years or 10+ years now.
Some of them will admit that their relationship has gone downhill to some level.
Yesterday, I was on my Instagram and saw a pregnancy announcement from an acquaintance's wife in my social circle. I don't particularly like her. I find it annoying to be around her the 1-2 times a year I ever randomly see her in person. Right now, there are 3 women from my local area social...
www.sosuave.net
There are some couples that exist today that formed a long time ago in a very different sexual marketplace. Many of them formed in the 1960s-1980s, a time where The Sexual Revolution was underway but it wasn't as ingrained as it has been post-1990. Some older Gen X'ers who formed relationships in the 1990s might still be together today. An example of this is Rollo Tomassi (in his mid 50s) and his wife, who have been together since the mid-1990s. Even the young adult Gen X'ers of the 1990s had a different sexual marketplace than post 2005 or post 2010.
In some longer term marriages, there have been affairs and emotional dependency.
I have observed this as well.
That's considered a success because of the marriage vow "Till Death Do You Part". Having a coupling of 40+ or 50+ years with a relationship ending in a death of one of the partners is considered the model relationship in the blue pill world.