No one gets oil tested so no one here can tell you whether it is a good thing or not. I ran a fleet of vans and trucks, all European and all Diesel, we changed on manufacturers recommendations, tested the oil and could have gone a lot further as the oils were all up to spec when changed. The truck supplier said they had run oils out to 75,000km with no detriment to the motors but they didn't like to as the mechanical checks were too far apart. My personal cars are all changed on specified manufacturer intervals and have never used oil between changes but I have never tested the oils, just observed the results.