[LorenPechtel]

It depends on how much you do it.

25 km/day, flat terrain, light pack--I have dietary issues that could prove problematic for a four-day trip (expending 4,000 calories in a day, not an issue. Consuming 4,000 calories in a day would be hard--I would worry about bonking) but I fairly routinely hike 25km in a day and with nearly twice his load (I'm typically in the middle of nowhere, if I have to push the button help would likely be hours away--my safety standard is I should be able to survive the night) and rarely less than 500m of climb over the day.