I've done three weekend trips to the US the past two years from Europe. Arrive friday, leave again sunday. Mostly using error fares where this was the longest I was able to stay, but also because I enjoy them even though short.
Just for the miles, I've also done a 4 hour stay in Chicago, routing OSL-ARN-ORD-CPH-OSL. Entire trip was 25 hours I think. Fortunately I do enjoy sleeping in SAS Business.