Hey, I'm the same age as you, (41F), and I'm in the same boat. I've actually never dated at all in my life until recently, and I've lived on my own since I moved out of my parents' place when I was 32. So, it's been just me for nearly a decade now. I really get that the idea of suddenly having someone "there" all the time can feel a little intimidating and disconcerting; we become very much set in our ways. But if we want to grow and get what we really want, sometimes we have to branch out and take risks.

For folks like you and me, I think if/when we reach that point, we'll just need to clear with our respective SOs about our history and be willing to communicate and compromise. Relationships require a lot of both of those, right? Not just with regard to living situations but in general. You may not wish to, but it may inevitably involve some give-and-take. If you have someone to talk to about all this (a therapist, a good friend, a relative with whom you're close, etc.) that may help some as well.

Of course, maybe you'll find someone who feels similarly and would accept the two of you living separately while maintaining a relationship? Perhaps some people do that.