My wife are around 30 years old. We are experienced trekkers (South America, Israel and Nepal), but in average-or-less physical shape - we're working in offices most of the time.
We have booked three nights in the Kepler track. Unfortunately, Luxmore Hut was full, so we have a very long day between Brod Bay and Iris Burn Hut:
Given the height profile:
Is it reasonable to walk from Brod Bay to Iris Burn Hut (approx. 22.8 km) in one long day?
Image credit: New Zealand's marvelous Department of Conservation.