Though not true timber frames, I have worked on a number of buildings with wood roof trusses in the 70-foot range. They were bowstring trusses built in the 1950's with split ring connectors. The designs were elegant for their simplicity and lightness. Analysis indicated that they were slightly under-designed by today's codes, but new trusses could easily be engineered to meet current code loads. Also, deflection was not much of a problem because the height to span ratio's were in the 8 to 10 range and stress goverened the design. The most recent one I looked at spanned 70' and the largest single truss member was a 3x12x14'!
Chris Hoppe, P.E.