Steve,
Myself, having never sold a drop nor used the full synth, I can only tell you what I have heard and seen.
According to the in house oil analysis lab in St louis Mo., they tell me that no, that the full synth normally doesn't extend out much farther than the blend counterpart.
The only time they normally sell the full synth is when a customer is having a really extreme problem with oil holding up due to really extreme temps and such beyond normal applications. And of course to an occassional few that can't believe the blend can do that well in comparison to the full because of what they see on the TD SHEETs.
I have seen reports where the Schaeffers blend used in OTR trucks, have done as high as 80,000 mile oil drain, but the normal is between 30 to 40,000k drains with an occassional 50k drain.
Let me throw this into the mix...
I have 4 shrimp boats currently running our moly bond 107 40wt. Normal oil changes with delo 400 was 250 hrs, with the moly bond, they are now up to 1,000 hr drains.