I really don't believe that 'functional' relationships exist...
I've gone through this with a couple people today. And the reason for me talking about functional relationships with friends is because two other girlfriends are falling out of their relationships and moving towards "finding themselves".
I guess that to be able to determine whether functional relationships exist you need to define what a functional relationship is and I don't think that's easy.
There's what society says is a functional relationship, and there's what actually is functional, and there's what each individual personally believes is functional.
The fairy tale (society's version of a) relationship: a husband and wife or boyfriend/girlfriend or the common-law couple. They are "happily" married or living together. There are kisses and hugs, some level of intimacy as well as trust and honesty and sex. There are bumps and difficulties along the way but they are worked out and the challenges make the couple grow together.
My best friend said that for her a functional relationship is one that shifts and changes with the people in it. The relationship itself will present challenges to overcome, and the individuals involved will also grow and change which will, in turn, create challenges to overcome. So challenges could be anything from cheating to money to sex... to whatever else couples fight and bicker about. They are constant. If any one or both of the individuals stagnate, or if the relationship (so the interaction of the two people) stagnates then the relationship will not work, or it will need a drastic shift.
It obviously includes all of that, although I had never really concentrated on that aspect of things. I think I can safely add though that relationships need to have two WHOLE people to begin with. Two people who know who they are and what they want in life.
The individuals need to be compatibile. This is one of the hardest things to find because compatibility is a vast pool of things: sex, trust, character, intimacy (which is the one I lack most in mine I think), social, language, customs, habits, expectations (this is a big one in terms of how a person views how relationships should be), work and hours, biological clocks, age, religion, race... and that's just to name a few. I'm sure I've missed some important ones too.
Sure, love can transcend many of those things, like age, religion and race but if you do transcend them in the beginning, they can come back to bite you. When they do, it then obviously ties into the changes and adaptation that couples need to face in a relationship.
There are other things that love can't transcend, things that are hidden in the beginning of a relationship that you realize aren't compatible with who you are until years have gone by. Things like social compatibility. Living in a relationship with a person from another social setting can be overcome short term but that can arise as a problem much later in a relationship. The level of intimate output or expectation of intimacy needs to be the same otherwise one person will always "expect" something more from their partner.
I think that managing to make all of these things work together is EXTREMELY difficult. It's a bit like looking into an old clock without being a watchmaker. You have all these wheels and cogs and mechanisms that you are trying to get to fit together and make them work.
Question is where do you draw the line and say this is functional enough for me, I will pursue the challenges the relationship throws me, I will grow with it? Or vice versa say this is not the right relationship for me, I cam not compatible with my partner, I am not willing to invest more precious time.