Spector,
You are indeed correct that lugging the engine - especially under heavy load - can increase bearing wear. Hard acceleration from low rpms is a particularly bad thing to do. Oil pressure is a function of engine rpms and you have fairly low oil pressure at 2000 rpms. However, keep in mind also that every rpm is a wear cycle, so there is a tradeoff here. For example, piston ring and cylinder wear correlates well to average piston speeds, which are in turn related to the stroke of the engine and the rpm range in which it runs. For this reason, high rpm engines are often "oversquare" designs, with large bores and short strokes to minimize piston speeds. If you consider the change in momentum that occurs at the top and bottom of each stroke, this makes perfect sense.
Some of the slowest wearing engines are medium to large diesels that run at low rpms. These engine also spec 15w-40 oils instead of 5w-20/5w-30 grades to compensate for the low rpm operation and provide higher oil pressure and oil film thickness.
For a given situation, oil film thickness is a function of the load between parts, the viscosity of the oil and the relative velocity between the opposing surfaces. A lower relative velocity decreases the oil film thickness. This is true for cam lobe/lifter oil films as well as for main/rod bearing films.
[ April 16, 2003, 07:11 PM: Message edited by: TooSlick ]