Never make comparisons with other families, not even those of your friends, In fact never compare with friends.
As others have said, every family is different - and we also get threads on GN from grandmothers struggling because they have to do so much childcare and their grandchildren are with them all the time.
As you say, you have a happy relationship with the parents, and that is the most important thing. You are fotunate that your grandchildren live near enough to see them so frequently. For those of us whose grandchildren live further away, we see our grandchildren a lot less than once a fortnight.