When You're Dating And Everything Is Separate. Is It Age?

via Le Love
This is one of those things that has literally driven me insane in the last year as I have repeatedly dated men that are slightly younger than me (insert future cougar joke here... go ahead....all my friends did it already).
Question: Does it actually make a difference if there is an age gap between you and the person you're dating? Does it make everything separate?
Now I know a lot of people would say: it doesn't matter as long as you have a lot in common, etc. and I guess I kind of agree with that. I mean, I started dating them after all didn't I? We have some things in common. The trouble occurs when we start getting into lifestyle.
So the person I'm currently dating and I do a lot of things separately and for the most part I think this is a good plan. Like for example, when he wants to do anything that I deem immature, I don't go. Or when I want to hang out with some of my couple friends, he doesn't go. Great. We both have lives. Way to be well rounded right?
Well now, we've gotten to this point where we have really separate things going on. All the time. And I don't know what's going on in his life in some areas and he doesn't in mine and I blame this on either a: an age issue or b: lack of proper balance. It also makes me totally crazy about the sections of his life that I am really not a part of since I had a set up like this before with a different boyfriend and when I dug into that separate piece of his life, I found really obvious cheating going on. So it's baggage city when it comes to separateness.
If it's an age issue, then why have I also dated men in their 30's that are hopelessly immature?
If it's a balance issue (which I kind of suspect) then where should the line be between your life and mine?
My friend in Brooklyn doesn't see her boyfriend for the whole week but then during the weekend they hang out for 2 days straight. It works for them. She does her thing during the week and he does his.
Another girlfriend suggested that we plan to spend one night during the weekend apart and one together so that we could plan to do our own thing during that night apart. But this sort of lead to to the current situation.
So now I'm attempting to integrate things the right way so that I don't feel suffocated by hang out overload or left out and separateness. What this likely means is: doing some things that I deem immature. This also means he'll have to do some stuff he doesn't like to be around me more. A few months ago I posted a photo of Frida Kahlo and Diego Rivera's house (remember, the house was actually 2 houses with a bridge connecting them) and I keep thinking about it now that I am faced with this issue. If things are that separate, how can you have a decent relationship?