Should grandparents be expected to care for our kids while we work?

Even though my parents live interstate, they never hesitate to help out with the kids when they can. It's something I definitely don't take for granted. I know a lot of families whose parents care for their kids on a regular basis, and some whose parents are not as involved. So should there be an expectation that our parents will step up and care for our children while we work or is that asking too much?  See omnystudio.com/listener for privacy information.