Originally Posted by Mike Jacoubowsky

Main thing that stands out is just three hours at Machu Picchu in that first example. Three hours might be all you want, but I'd plan on 5-6 hours and simply leave early if you've done enough. If it's just a place to check off the bucket list, fine, 3 hours and move on to the next. But it might captivate you. If it does, how will you feel about having gone to so much trouble to see it, only to have to leave so quickly? It's not that one way is right and the other wrong. Many people do a 1-2 hour tour with a guide and no exploring on their own, and that's enough. Others want to get out on the trails and explore, and you may very well want an hour or so of "downtime" in-between long-ish hikes. Add extra time if you want to climb Huayna Picchu.

If you're not into hiking, stick with the shorter itin at Machu Picchu. No need to torture yourself, and there's no water or food stands out on the trails. But if you're unsure, then take one of the early busses up the mountain and plan on returning as late as 2pm. That would allow up to 7 hours on top. If you're done with the place in three hours, return to town early and have a nice meal, see the town (it's not very big), visit the shops.