Black Forest Trail is a beast. Very difficult climbs and descents. I would not recommend that for a trip just released to hike again. 42 miles of nothing but hills. It is a great challenge. The Susquehanock trail system is a real possibility. 72 miles. Only one very difficult climb from what I understand. I've done bits and pieces but not the whole thing.
edit: Lots of bail out loops and cross trails so if things get hairy you can cut it short with a fair amount of ease.