I climbed the O.S. with my son about 14 years ago, when I was 52. We took a rope and harness but never pulled the rope out.
I was in great cardio shape, back then and we were on the summit by 9.30 A.M, after leaving the parking lot at around 5 A.M.
Last summer, after coming out of the Wind Rivers, I spent a few days at the climbers ranch. On my last day there, I decided to to hike up as fast as possible. I got a very late start, (Noon), for a variety of reasons, but still managed to make it up to the lower Saddle in 3 hours.
All the advice about cardio training is spot on. Last summer, I was training , by hiking Mt. Washington or Chocurua every week, as fast as possible. It payed off big time on my trip to the Wind Rivers, trying to keep up with 68 year old Jim Donini.