21-m Roller Coaster AT hike

I woke up 5:15 am to carpool for a Full 30 mile Out-And-Back Roller Coaster hike on Appalachian Trail in 15f. However, four out of six hikers (including me) turned around and finished 21 miles with 6000 feet elevation gain, while the remaining two hikers probably hiked with headlamps and got back at 9 pm. I could barely caught up with the fast hikers so no time to take more photos. It was sunny but cold so I used hand warmers inside my gloves. I did the full hike twice before in summer yet after several longer distance hikes to condition my body. But I did not do enough 18-25 miles hikes this winter to finish 30 miles today. Another concern was shorter day night in winter and I avoid hiking in the dark. I was and still very tired from hiking the 21 miles.