I saw a special on the USAF PJ's.... It stated they were going to be covering 60 miles per day in full gear.
A very good friend of mine is a PJ- way I heard it from him was 60km. Still a good haul on broken ground and with full kit, but doable if you aren't (a) worried about setting camp, (b) know you can crash shortly after you get there, (c) prep for it, and (d) are trained that hard. But you can't do it for a prolonged period.