I think you need to be best friends with your partner.

I also think a relationship cannot work out between people who do not have a basic respect for other humans, and who put their "wants" first. Dunno how else to express it.

I've lived with my DBF for the past 10 years, together 11.5 yrs.
We would probably be married if there wasn't the tax hike you suffer when you do, as we both make a full salary. I don't want kids, although sometimes I fear I will regret it, but then the "minuses" come back into focus.
We've talked it through, I think he could envision them but I do not think he would cut back on his career so it would be me bearing most of the load.

We have never had a fight. He supported me through some rough times.
Once I was whining about the job when the previous one was the job from hell (&above-said rough times) that I just got out of, and he got exasperated, probably thinking "there she goes again" - I realized what I was doing and told him that I did not expect him to solve my problems, just to listen and pat my head saying "I understand".

I need to have a partner that I can look up to, in part at least, intellectually. That does not necessarily mean he has to be better educated, but he has to at least be mentally agile.

The physical part of a relationship, I think, gets overrated and after 10 years, we are in a comfortable, low key kinda rhythm that suits me. Physical closeness is much more important.
We've talked about that as well. He's not good with expressing emotions but I told him repeatedly that he must bring it up if something's not right. Hope he will.
He is the loveliest person I know as a type of guy, he loves cooking, etc.
I think you need to keep up gestures of love to keep the fire crackling. So I try to sneak in little things, sticky notes when I'm gone unexpectedly, etc., go out and have a drink before dinner -
And his body is looking better than ever with starting triathlons as well :-P