FWIW, I run M1EP for ~12k between changes both in the 80 and the 100, change both vehicles every February and sample each change w/ Blackstone.
Anecdote: I've had my 80 a long time. After I drained the oil from the 80, I would put the used oil into my beater commuter car, a 1996 Ford Probe. Started doing this in 1999 when the Probe was 3yo. Sold the Probe last year (2011) at ~260k miles and drove like the day we bought it. 37mpg as long as you didn't turn on the AC, what was I thinking?
In total, every quart of the EP probably got 20k miles use.