Writing time

If I'm serious about writing for a living, how much time should I give over to writing? Probably more than I should. But the trouble with working full time and having a family to take care of is that writing gets pushed to the bottom of the pile. There's often something else that I should be doing, washing, ironing, hoovering, cooking etc etc. It's not exciting but it has to be done and it's part of being a wife and mother which is afterall my first job. (Just kidding it's not a job it's a pleasure - yeah right, ironing is always a pleasure.)