I retired years ago, but once we had radar I always had it on mapping (If nothing more imminent) over long ocean crossings.
Other pilots asked why did I have it on if there was nothing to see and I had to recount the RAF aircraft that didn't because they were routed well south over the pond to the USA and there would be nothing to see.
Unfortunately they weren't "well south" when they thought they were and in response to a confused navigator practicing grivation...turned it on. They immediately saw what they thought was a large ice mass...which it was, but unfortunately the one that covers Greenland which should have been many hundreds of miles to the North. They just made Goose Bay!
So if you are not using it for anything else, why not have it on mapping so that where you should have nothing on track...you can see that you really don't.