Live very locally to one set, think walking distance (1) , quite local to another (2) and the third set live literally a few streets away (3. divorced parents..)
1 - atleast once a week, either at our home or theirs. They frequently babysit. We often just pop into their house for a cuppa, or when I just need a breather with the kids.
2 - again at least once a week, usually the same day and they take the kids for a few hours. Often see them outside of this too.
1 & 2 have key access to my house and me theirs. They are a fantastic support system.
3 - due to family falling out no time is spent with them. It's difficult and a sad situation.
Every family is different and there is so much to factor in (work, retirement, school hours, travel etc) Also a bit of come and go if possible, you got to them and they come to you or you meet up somewhere either routinely or spontaneously. If it's comfortable to you seeing more of the grandparents can be a great support system.