I did the GAP in May in 2.5 days from McKeesport to Cumberland, then another 1.5 days on the C&O to Hancock. The GAP is a wonderful trail, crushed stone surface and very well graded and maintained. It's uphill all the way from Pittsburgh to the Eastern Continental Divide, but it's so gradual that you hardly notice. Then you ride through the tunnels near the divide and blast downhill for 20 miles to Cumberland. The GAP goes right through some towns, so I never carried more than 2 days worth of food. It goes through Ohiopyle State Park too.
Oil is good, grease is better.
2007 Peter Mooney w/S&S couplers/Terry Butterfly
1993 Bridgestone MB-3/Avocet O2 Air 40W
1980 Columbus Frame with 1970 Campy parts
1954 Raleigh 3-speed/Brooks B72