My "birthday marathon" (reported in http://www.snowjournal.com/discussion/1299/crotched-mountain-2017-2018#latest) yields the question, where, besides Crotched Mountain can one ski 70 or more runs in a single session.
Places like Stowe and Wildcat with high speed chairs that rise 2K vertical allow for 100K vertical days, but with much less than 70 runs.
The combination of the high speed lift and the length of time that the mountain is open are what make this possible at CM. I can't think of another area in the east (over 500 feet vertical) where one can get that many T2B runs in a single day as one can get at CM.
So: what other areas (in the east) offer the opportunity for 100K+ vertical or 70+ runs in a single (regularly scheduled) session.