Certainly possible for a woman (or man) to ask for it - it's called a joint lives order and is essentially about preventing undue hardship (basically keeping someone in the manner to which they've become accustomed). Maintenance for children is a separate issue, the joint lives order is about spousal maintenance. I don't think there's even a set number of years that you have to be married before you can ask for it. I find the idea of a couple being married for a few years then one being able to claim maintenance from the other for the rest of their lives pretty horrible to be honest but that's just a personal opinion.