Some of mine through the years have been solely for the purpose of making the hike longer and harder...!
These were all day "hikes."
New Russia - Rocky Peak Ridge and Giant - Chapel Pond - Round Pond trail - all the Dixes (missed Macomb because I ran out of water) - out to Elk Lake.
Colden, Cliff, Redfield, round trip from Elk Lake.
Loj - Algonquin - Avalanche Pass -Trap Dike - Colden - down Lake Arnold slide - Marcy - Loj.
I love that kind of thing, and just wish I had time to do more of it before something finally breaks.
But of course folks like Ed Palen, Sharp Swann, Ted Kaiser, and Jan Wellford are the real masters of the strenous link up. And they come back and do it again the next day, and the next...
I want to get into summer ultralightpacking (10 lb overnight pack), but it will have to be solo; it's a hard sell on the home front.
I have not read of anyone trying to set a time for an unsupported NP Trail through trip. Tim's record time of 37 hours or so was a supported, full time run. I think an unsupported trip would have to take at least 60 - 70 hours. You'd need a water filter and at least 4 or 5 lb. of high energy food, probably a total pack weight of at least 12-15 lb. I don't think you could run full time with that, and you'd have to bivy at least once, maybe twice. That's a good challenge for someone...
Tom