I know what you mean Tiger, I am having this exact dilemma at the moment too. Your natural feeling is that things should be moving along somehow, but with all the logistics to consider, it doesn't always move in the way you expect, like it did in the first big relationship.
Only last week (at couples counselling) I said that our relationship is actually no more committed than it was a week after we met 6 years ago! We both still have our own homes, where we live with our respective DCs, we don't share money or responsibility for each other's homes or DCs, he spends a few nights a week at my house, but doesn't contribute financially and I rarely go over to his.
Spending time with all the DCs together is stressful, we parent differently and I'm an introvert so need quiet time to unwind. We have looked at moving in together previously but it just caused arguments between us and between the DCs, so we abandoned the idea.
I just feel stuck in limbo, waiting for all the DCs to grow up and move away (which realistically could be 10-15 years away!) until we can move on with our lives together. I think he would be happy keeping things as they are, the pressure to progress comes from me really.
I want to be married to him and to share our lives. I already take care of him, cook meals for him, listen to his work woes etc and he gets the benefits of my emotional support and love, just like a wife, but then he earns ten times more than I do and I don't get the benefit of him as a husband, so it feels a bit one-sided if I'm honest. Its like a two-tier family, with him and his DCs reaping the rewards of his lifestyle while me and mine struggle financially and I have to do all the donkey work of running a home alone (he has live-in help with his DCs and house).
I would like to feel like we have an equal balanced partnership, but we don't and never will have while our lives are so different. And it isn't just financial, its about feeling emotionally connected, having a shared goal, looking to a future together, how much spare time/energy etc we each have too.
Keeping things separate is all well and good if you are both happy with your lot, but when I was down to my last £3 and he turned up with a brand new £40k car he'd just bought with cash, I couldn't really muster the enthusiasm he thought it required!
It's really tricky once your lives are already so established in their own patterns, but it sounds like he's happy with things as they are for now, so any progression probably won't be 'natural' - it will have to be forced in a way. Do you feel like you could talk to him about what you both see in your futures? Whether you're both envisioning a similar lifestyle once you're free of parenting responsibilities etc. Do you share values generally? ie how you handle money, how you like to spend free time, how sociable you are generally etc.