I find the DPs who have GM to do lots of childcare really don't appreciate it- it gets taken for granted over time.
Oh yes!! My sister used to leave her two children with our mom for 13 hours a day each week. Our FT working mom then had to work her 37.5 hours over the remaining 4 days of the week. She was exhausted but my sister seemed to have no comprehension of this.
Our mom initially had my sister's DC1 DS from when he was 10m old and two years later, when my sister announced she was pregnant with DC2, my mom said to me, "She'd best not think I'm providing childcare for the next one too."
She also said something along the lines of this to my sister too but when my sister returned to work after maternity my mom did end up having both children as my sister just assumed it would happen and my mom felt too guilty to say no as she knew my sister would struggle with childcare fees for two and she couldn't see how she could agree to having one DC but not the other.
In total my mom provided this state of childcare (and the resulting compressed working hours over 4 days) for about 6 years in total and then she had to tell my sister she just couldn't handle it anymore.
My sister was then more concerned about the extra childcare cost than how tired our mom was.
Once the arrangement stopped my mom was able to work her FT hours over the usual 5 days instead of 4 and she was much better for it. It was a really awkward situation.
When I had DS I said to my DH that in absolutely no circumstances would I be asking my mom for any childcare. She'd "done her bit" in terms of childcare as far as I was concerned and I certainly didn't think she owed me the same childcare that she'd provided for my sister.