I agree. I've been with my DP 7 years. We don't live together for various reasons, one of which is that we don't want to uproot the DCs, as they have their own friends at their respective schools and if we moved in together one set of the DCs, if not all of them, would have to travel to spend time with their friends.
By trying to be considerate of our DCs we are apparently not serious about each other. Both sets of DCs have their other parent living locally, so they would end up being further away from them too, which would make their life less convenient.
It's just daft that we're berated for putting our 'sex life' before our DCs when we do move in together, and told we're not allowed to say DP because we're just BF and GF regardless of how long we've been together, if we don't.
I'd like nothing more than to be able to afford a big enough house for us all, without putting too much pressure onto DP, but with 3 DCs of my own and 2 of his, the cost of keeping us all would inevitably end up mainly on his shoulders and I'd end up losing child benefit and working tax credits which I get for being a single mum on a low income, so I'd bearing the brunt of housework for 7 of us instead.
So we'd end up with a less convenient location for everyone, with less disposable income between us, more stress for him and more work for me. Where's the incentive?! Just so that MN could agree that he's actually my DP? I'll stick with my own space thanks, and he can keep his and we can get together whenever we choose and retreat to spend time with our DCs when we choose.
That doesn't mean I'm keeping an eye out for someone better to come along or that he's just using me for sex, it just means we realise that we're not the nuclear family we all set out to create the first time around, and we're making the best of where we are.