Clint· Super Moderator
I'd think those with a synthetic factory fill may have an even tighter tolerance to do so.There is no reason not to switch right away. Modern engines are built with much better tolerances than days of old, and many engines come with synthetic from the factory. I have not seen anything other than anecdotal evidence, ancient advice, and recommendations for rebuilt engines that suggests otherwise.
Maybe call an engine builder and get a current day expert opinion on the subject?