balls vs. rollers
Tapered roller bearings have too much sliding and skidding going on, I believe it is impossible to eliminate 100 percent. It is hard to trust them at high rpm for long period. They also have roller edge stresses. Balls run so nice and smooth. Cylindrical rollers run nice too. I don't understand why they use so many rollers in the engines, when the bearing that carries all the engine trust is a ball bearing. I would think the thrust bearing would need replacement before the radial load bearings, which will have a far greater life both from reduced load. Balls have a little sliding going on too under high loads. My gut feeling is the lube is mostly working on this area, adjacent to the high stress contact area. Contact area is left with microscopically thin lubrication thickness.
What amazes me the most is how small the main thrust bearings are, how few balls it takes to transmit 80,000 horsepower. I once had a 5-axis 15 horsepower Matsuura machining center spindle apart. That seemed to use bearings about 1/3 the diameter of the Trent 900, and about the same quantity. This machine could make a barrel of Hastelloy or Waspaloy chips in a few hours, so enough power to cut anything fast. (Machine not for high speed high horsepower easy cutting aluminum however).