Well, to each their own I guess, but I agree with the others, I hardly think once or twice a month makes you a bad mum. Everyone has different opinions on the matter, but how I feel about it is, before I'm a mum, I'm me - and I have to take care of me before I can take care of my son. My MIL has my little boy once a week. That one time a week I do things for me - paint my nails, catch up on things that need to be done, SLEEP, etc. When my son comes back home I feel energised, and I feel like I'm a better mum. Now granted some women can go 24/7 looking after their children. And that's fine, but again, everyone is different and I think it's really horrible for someone, especially family, to chastise you for having a bit of time for yourself.
Beginning in October, my son is going to also be in nursery 2 additional days a week so that I can do my final year at university. Again, don't think that makes me neglectful or selfish, quite the opposite actually. I'm continuing in education so that I can provide the best for my son.