Oils are better, Fuels are better, and engines are better than they were in the past.
All 3 of these things allow oil change intervals to be extended. The question is: By how much?
Most Service Intervals are optimized by car mfgrs. for marketing purposes - to make the cars easier to sell.
But, most manufacturers, incl. Porsche state in their owners manuals that these intervals are for Ideal conditions, which almost no one encounters. TRhey further usually state that for Severe conditions, these intervals should be shortened. Because they cannot know everyone's driving habits, they cannot say by how much, since each one's experiences are different.
Frequent short trips (under 10 mi.), Stop&Go driving, Interstate driving, wet climates, dry climates, hot climates, driving past construction zones or projects, poor or eratic fuel quality, hard driving, heavy loads all constitute what automakers term Severe conditions.
So, it's safe to say that going 20k mi. between changes is not recommended, even by the carmakers themselves.
You need to use your own judgement. 7500-10k mi. covers the bases pretty well, you are doubling to tripling the previously accepted interval.
But, you really need to consider the interval differently for each batch of oil you use. If you have a rainy season, or hot season, or any changes during an interval, say driving hard, or your daily route is under construction, you may want to shorten the interval. Likewise if any of your normal conditions change for the better, you could extend an oil change a few thousand miles too.
Just remember the old addage: "Oil is cheaper than engines"
