I seem to recall Porsche going to 30k mile intervals, but I believe that they had a shorter filter interval. Of course, they were using a synthetic. My understanding is that this was a move to make their cars more environmentally friendly, and I'm not sure whether engineering approved, but the manufacturer only really cares about longevity for the duration of most leases or initial ownership periods (obviously a reputation for longevity helps sales overall, but if they're going to cut corners they're going to focus on initial ownership satisfaction).
IMO there's no point in discussing oil change intervals unless you have an oil analysis (e.g Blackstone Labs) to prove the condition of your oil.
I don't know any modern brands that are using non-synthetic oil.
That is not a good idea if you want your engine to last.