I've never personally known of anyone that had an oil related failure at under 200,000 unless they ran out of oil. Lots of those guys/gals changed once or twice a year at most.
I think the most important thing is to just keep oil in it.
I've seen multiple oil related failures, as early as 65k miles in one case, many before 100k. Of course, they are uncommon, but since I'm in the repair business, and have 5-15 cars a day through my shop, it's not surprising.
They are mostly failures due to a lack of oil changes, not the fault of the oil itself. Everything from seized cam bearings, to variable valve timing mechanisms, to oil pressure loss as a result of contamination and sludge formation. Synthetics are not immune to this, or at least Class 3 synthetics like Castrol. Don't see it much with Mobil 1 though. Had more than a few that are subjected to the 20-25k change intervals, have oil filters that are removed in pieces from the canisters, and when valve covers are removed, are so full of sludge that the only bare metal visible are the cam lobes. Everything else is covered in a thick layer of gritty goop.
