My wife went 8,000 miles on PYB once.
I hadn't been in the car for a few weeks and when I saw the trip odo, I went nuts.
Changed it immediately with no negative effects.
The 3.5 liter V6 in her Toyota Sienna was known as a sludger.
But PYB protected it through my wife's neglect.
If there is a positive case for synthetic, it's that you can get away with a mistake like that without worry.