I've been able to receive some ARTCC RCAGs from 40+ miles away, as they were located on mountains that were 1500 higher than the area I was in. Then there are others I can't hardly pick up from 7-8 miles away. Terrain is the biggest factor, since unlike most land mobile services, the antennas aren't that high off the ground and are designed to radiate most of their energy upwards a couple of degrees.
I live in South Florida where terrain is pretty much flat and any altitude over 24000 I can get from 160-240 miles depending on that altitude. 10000 feet I get from a good 120 miles out. Mid altitudes I get about 160 miles. 24000 at about 170 miles all the way to 35000-43000 feet a good 230 miles. When I lived in a pretty mountainous area in NJ the most at high altitude I recieved was 170 miles.