My MIL watched our oldest daughter full-time for several years, although she started preschool when she was 2 1/2, so at that point she wasn’t with her all the time anymore. When we had our second child, I started working part-time, so she just watched the kids part-time. Now she watches our 3 kids 2 days a week (though the oldest is in school and the middle one is in preschool, so they are not there all the time.) My FIL is usually home from work on one of those days, and my mom comes over for awhile on the other day to help out, so it’s rarely just my MIL watching them by herself. We are expecting our fourth baby in December, and we will use a home daycare for one of the days that I work, at least for awhile, so that it won’t be too overwhelming for my MIL.
Anyway, having grandparents watch the kids has worked for us, since we only need childcare two days a week, we have both sets of parents nearby, the older two are in school or preschool, my husband has a flexible schedule and can leave work early to pick up our oldest from the bus stop, and I can work from home if I need to. Also, our parents are in their 60s so they are not elderly, and they are still capable of watching them.
I don’t think grandparents are obligated to watch their grandkids. Sometimes they are not physically capable of doing so. Sometimes the request might be unreasonable, such as wanting grandparents to watch 3 kids under age 4 for 40 hours a week. But I have to say it sounds selfish to refuse to watch your grandkids AT ALL for no other reason than you’ve “done your time.” If I was retired and still in good shape physically, I wouldn’t mind watching my grandkids some day, probably for a maximum of two days a week. I wouldn’t want to do it full-time, but I certainly don’t think two days a week is a big deal, especially after you’ve experienced four kids 24-7! The grandkids go home at the end of the day – it’s not like I would have to get up in the middle of the night with them. I would still have plenty of time for my hobbies and other pursuits. My in-laws sing in the church choir and have traveled all over the world. My MIL is in some other church groups too.
Also, when our parents are elderly, my husband and I can help them out more, by taking them to doctor’s appointments and on errands, helping them with chores, etc. We are so lucky to have so much family nearby. We all help each other out.