In normal use, I've never lost an engine due to occasionally stretching the recommended oil change interval out a little.
Occasionally stretching oil change intervals out a little as you say probably will do no big harm, however a steady diet of extended oil changes will. It will cause head gaskets, main seals and other engine components to wear excessively. What constitutes "occasionally" and how many miles is extended is arbitrary to many. Oil is cheap, engine repair due to oil change neglect isn't. I don't see the logic in laying out tens of thousands of dollars for a vehicle only to cheap out spending a few bucks every three to six months protecting your hard earned dollars. You guys can do what you want, I am changing my oil every 5000 - 6000 miles using Mobil 1 synthetic. If I were using conventional oil it would be 3000 - 4000 max.