Unfortunately I haven't had time to do longer than a 1 hour at a time listening session, so not long enough for fatigue to set in. However, with my HD800 and a DACmini I'll start to feel fatigued within 3-4 songs. So, this is actually still a good sign that 1 hour is safe so far. I'll have more time this weekend to go longer, but I will usually still take a break at least every 2 hours. I don't have the endurance that I did when I was younger.
For listening to music I mean
For active listening I rarely go over 1-2 hours without a break so that sounds good. Any hotspots on your head with the headband by the end of your session? It looks wide enough (forward to back) to spread across well.
Thanks for quick reply.