I do not claim to be a race winning fitness buff. However, I certainly feel that any reasonably fit mountain biker should and likely does do 2 hours of technical climbing quite often with great enjoyment and minor strain. I also know riders well into their 70’s who ride human powered bicycles for hours on end. So, I’m really not sure where you are coming from saying that 2 hours of climbing on a bicycle is some great feat. Check in with some riders on Fromme or Seymour on a busy Saturday and I think you’ll find that most them are spending 3+ hours of fun, human powered, cycling.