It all began with a hike up Mount Wachusett when he was 16. Since then, Philip J. Carcia, 24, has managed to hike all 92 miles of the Mid-State Trail in Massachusetts, the 275 miles of the Long Trail in Vermont, and is now more than two-thirds of the way through the Appalachian Trail. “I heard about the AT (Appalachian Trail) when I was 17 or 18 years old,” Mr. Carcia said. “I was seduced by the idea of going into the mountains for days or weeks without re-entering society, so I put it on my list of things to do.”