I have been living with mine for almost 3 years.
We were both fresh out of marriages. We fancied eachother slept together a few times, then feelings got involved. So I backed off. We stayed friends for a while, then it started up again. But we still didn't want to be an official couple.
But honestly, we were. When I got my house post divorce, he helped me move in a decorate. Got it set up for the kids. We spoke on text all the time. Any nights my kids werent with me, we stayed together. Any days off we had together with no kids, we spent together. We even did our weekly shop together. Neither of us saw anyone else.
I, actually, posted here because I was going to end it. I knew I loved him but was scared. I explained the above and some lovely mn'ers told me, nicely to get a grip and it was obvious he wanted to be with me. I am grateful that they did.
But it took a couple of years beginning to end. And we were at the same stages together. At the beginning he was what I needed. Good sex, an ego boost and a friend that understood what I was going through. And when I needed/wanted more so did he.