For me the only remotely logical 6-month change would be to drain the fresh oil out of the engines in the spring, after hibernation, then put it in the other engine.
No that doesn't make any sense, and that's why I don't do it. Or dump the fresh oil in the spring only because it has spent some six months in an oil pan instead of in bottles.
But I have thought about just draining the oil in the fall, then not filling the engine until spring. That might appease some who believe strongly in the 6-month rule.
