Okay, so admittedly, despite being in my mid 30s, I have zero actual experience... But, if I were in a relationship, I think I'd just want it to be like a very best friend, who was close to my age, wanted the same things from life, & wanted to be exclusive sexual partners. But, at the same time, no dating, no marriage, no kids, separate houses, separate bank accounts, &, just in general, not spending too much time together. Not sure if that answers your question or not, but that's what I think it would be like for me. XD