Like most things here, it depends. For example, I own a VW TDI BRM, and the rec OCI is 10k. With that, I have read data suggesting that reducing this OCI will actually increase wear. I believe the conjecture is soot in suspension provides part of the protection.
On the flip side, I also have a 996TT, and the consensus there is changing in 3-5k due to turbos, heat, IMS, etc. This is well below the factory suggestions.
Finally, my wife has a Tiguan, and the rec OCI is 10k. Given some of the problems Ive heard about sludge in Audi turbos, I change at 5k.
In a perfect world, an alarm would go off telling us that optimal protection is passed, and the onboard computer would give us an infallible message regarding what oil to put in for optimal protection. Unfortunately, no such device exists, so we are relegated to best guesses and lose empirical interpretations. That's one of the reasons for these forums I suppose...