A few years ago we took our most difficult hike. The Seven Devils Loop Trail in the Hells Canyon Wilderness of Idaho. It's listed as a 26.7 mile trail; however, with some trail additions and a 9 mile day hike we added near the end of the trip, it ended up being approximately 42 miles over 7 days.
It was the hardest thing I've ever done in my life. We had enough food and equipment, but I was not mentally prepared, at least for parts of it. The previous hikes we had done were at a moderate difficulty level, at best, and this hike was classed as strenuous.
We survived it, learned from it and are looking forward to our next hiking season.