Yes, I know quite a lot of families around here who have a full-time live-in nounou - it's a way of buying their freedom even when they are parents to young children.
My partner's ex has absolutely no qualms about using other people to babysit her sons whenever it suits her - the latest proposal (quickly squashed by me) was that I might like to take care of my stepsons for six weeks while she does a (totally optional) professional training course . She finds it very hard to grasp that my partner and I aren't at her disposal to take care of the boys when she feels like it.