DH and I don't get out just the two of us all that often, maybe every 8/10 weeks. We both work ft so at weekends we tend to do family stuff, days out with the dc, socialise with other friends or family and their dc. Or just veg out at home.
I have lunch or dinner out with dm and dsis once a month or thereabouts and with various friends 2/3 times a month though that could be twice in one week and nothing for a fortnight...
Agree with Ragwort about having an identity that's not just about being someone's mum. I think it's fine and actually good for dc to see their parents as individuals who have their own interests and friendships as well as being the dcs parents.