This is my second long term BDSM marriage. I was married to my last slave for 6,5 years. This one is 1,5 years, and married since August. It's going really well. Last one went well to. We just grew apart.
I think it removes many unnecessary conflicts. Most decisions in life are pretty arbitrary and the important thing when you do things as a couple is usually not what you do, but who you do it with. But that said, I think there's a strong genetic component.
Some people just are dominant by nature and can't function well in a non-D/s relationship. I can't. I get accused of all kinds of stuff which I don't even realise that I do. I do think I'm sensitive to my partners needs. But it's on a different level preventing me from noticing minor things. It's really beyond my conscious control. I've worked on it all my life, but I'm an idiot when it comes to making certain emotional connections. I automatically map my partners needs and think for the both of us making sure she gets what she's indicated she needed earlier. I tend to forget to ask people what they want if I already know it. This annoys non-D/s people I'm not in a hierarchical situation with.
My wife tells me of a similar situation for her, but of course opposite. She's naturally submissive and has told me she tends to get taken advantage of if she doesn't constantly fight it. She's a bit disorganised when it comes to certain practical things and seems to need somebody taking control. She seems happy about it. Very happy indeed.
Sure, it could be learned behaviour. That we have copied behaviour patterns from our parents. But then again, they might as well have had the same genetic predisposition we inherited.
To sum up. If I'm just myself making minimal effort in a relationship, I'll be a dom. And my slave doing the same will be a slave. For us a BDSM relationship is undoubtedly the preferred form of relationship and the most stress free. But I don't for a second think this is a universal thing. I strongly doubt it. I think when it comes to marriage, there's no one perfect form of relationship. I think it's very personal and I think there's a genetic component which we do best in not fighting. If we do we're just setting us up for misery.
That is at least my theory.