I was a regular visitor for work purposes, back in the day. I remember one day the plane back wasn't until late afternoon and by mid-morning there was nothing left for me to do until it was time to go to the airport.
So a colleague said I could borrow her car for a couple of hours - so I did and drove to the Ring of Brodgar and for an hour or so and I had it all to myself - it was a wonderful way to spend an hour.
If anyone is inclined to go (post- Covid) you shouldn't miss Skara Brae and, of course, Maes Howe.