My in-laws did move, but as mentioned only after their health declined. Prior to that they would visit regularly.

My parents have so many reasons for not moving (Of course they want to see their grandchildren; they fly out 2-3 times a year and we visit every summer):

1. My dad only retired a year ago, and he still occasionally works on a contract basis

2. Which kid do they move to be close to; me or my sister? I'm on the west coast, she is in flyover country.

3. Having lived in the area for over 30 years they have many close friends and are actively involved in the local community.

4. Moving to either me or my sister would put them much further away from my maternal grandmother, who is in her 90s (right now only ~400 miles away from them).