I've been around engines of all kinds for many years. I have never heard that switching oil is a problem. Never. If switching oil was bad, every car, motorcycle, tractor, truck, etc. maker would refuse to warranty their engines if oil was switched. As far as I can tell no maker in the world has ever done that. Other than specify oil grade they couldn't care less.
He'll in my cages I don't think I've ever put the same oil in twice, I buy whatever is on sale. In the bikes I am a little more consistant, not because of any potential damage, I can just feel/hear a little more of a differance between oils.