I found that the DC range of headsets gave me a headache after about an hour, and put this down to a mixture of the clamping force and the fact that I wear glasses. I ended up with a Peltor headset which has given me over ten years of excellent service and although not as good at noise attenuation was much more comfortable. Earlier this year I took the plunge and bought Bose headsets for my partner and myself. These were very expensive, but are superbly comfortable with excellent noise suppression and much improved RT clarity. I've worn these for several hours of flying at a time without noticing any fatigue problems. The only problem is remembering to have a spare battery with you because the passive attenuation is quite poor.