PHL and LGA have some great "early arrivals" into outer stations WHEN there are no ATC/WX problems there. However, it is more common for these flights to arrive closer to skd than arriving very early.
If and when they ever debank PHL, the flight times from there can be adjusted accordingly. I've been keeping track of the 845 am dept from there, and its feast or famine. The other day it left the gate about 10 mins late (missing its normal spot in line) and arrived about 5 mins late after close to an hour taxi time. Another day it left a couple of mins early and made it in about 25 mins early after only a 20 min taxi time. There is such a wide variation, especially in PHL, of actual times, that I'm glad they currently have the flights padded as much as they do.