So you have ridden the GAP/C&O trail(About 330 miles), both ways and are no looking for some other multi-day rides.
May we suggest some. These typically have one long segment and several side trails, so you might want to consider doing an out and back ride.

Armstrong, Redbank
Rosston to Brookville 66.1
side trail to East Brady 4.4
side trail Sligo spur 1.0
side trail Cowanshanock Falls 1.0
total trail miles 72.5

Ghost Town, Hoodlebug Trail
Ebensburg to Indiana 43.8
Side almost loop Vintondale to Nanty Glo 13.0
Side trail to Route 22 2.7
total trail miles 59.7

Allegheny,Samuel Justis, Oil City, McCormick, Oil Creek State Park, Titusville
Emlenton to McClintock Well 38.1
side trail Sandy Creek 14.9 miles
total trail miles 53

Gasper Caperton, Deckers Creek
Reedsville to Fairmont 42.5
side trail to Port Marion 11.3
total trail miles 53.8

Butler Tredway Trails
Butler to Arnold
side trail to Kiski Bridge
total trail miles 37.4

West Penn, Westmoreland Trails
Blairsville to Delmont 21.7
side trail North of Saltsburg 2.0
total trail miles 23.7