I think she is getting flack because she makes so many assumptions. I am quite cross with my own DD at the moment because she has assumed that, at a family wedding later this year, I will be happy to toddle off to bed early with the kids while she goes on to a specially-booked nightclub after the main event. I quite like the idea of a bop, aged and infirm GP that I am... 
But her MiL, who lives close to her, is amazing. She never minds how many of her GCs she looks after, or for how long. I think she's mad.
I like seeing mine for weekly blocks, but would hate to have them on a weekly basis. I know I would feel too tied, I did feel tied by my own children, so I wouldn't want that again. I have several friends who care for their GCs and it does seem to cause consternation when they realise they have had enough. The parents seem to take it very personally.
I heard my next door neighbour's Mum shouting at the twins (
) for several days in a row. I saw my neighbour and gently asked her if she didn't think her Mum might be finding it a bit much. They are now three and she has had them since they were born. My neighbour kept on asking, why, but I wouldn't say more. Within two weeks they were booked into a nursery every morning and now Grandma only has them in the afternoons for a couple of hours. No more shouting. I for one am very happy with the new arrangement and Grandma looks ten years younger.