Is there a way to prevent (not relieve) the hotspot caused by wearing a headset for long periods of time? About a year ago, I bought myself a Bose A20.  Within two weeks, I had returned it.  

I will be the first to say that the noise reduction for the A20 was fantastic.  The headset was amazingly light, and clarity was superb.  The reason I returned it was because after wearing it for an hour or two, I would start feeling a sharp pain on the top of my head, where the headset rested.  I'm not the only one to have this happen:


  Unfortunately, I have decided to return these headsets in the 30 day trial period. After the first week, these headsets started to "hotspot" the top center of my head and became uncomfortable after several straight hours of continuous flying. The sound quality was excellent but it came down to a comfort issue. There were a few annoying things.


Here's another...


  On one trip the airplane was equipped with a Bose headset and I thought I would let my wife use it. After 1 hour her head had a bad hotspot and she made me switch. After 30 minutes wearing the Bose I too had a hotspot.


And a quote from the A20 owners manual:


  During a long flight, you may feel a slight pressure point, which can be relieved by adjusting the headband position. Your experience with using the headset will help establish a sense of how it should sound and feel.


I wanted so badly to like that headset (in fact, I still do).  My faithful David Clark will be heading back to the factory for repair soon, and I'm willing to give the A20 another chance, if there's a way to keep that top-of-head hotspot from forming.

Is there a way to prevent (not relieve) the hotspot caused by wearing a Bose A20 for long periods of time?
The best way to prevent the "hot spot" pressure point from the headset band is to wear a headset that doesn't have a top band (like this or this). Of course this requires that you be able to wear an in-ear headset, and some people are more bothered by that than by the headband.

Short of wearing in-ear headsets there are numerous different headset band pads you can try - I know at least one person flying with this sheepskin pad.
Some combination of the right headband position and the right pad should make your headset more comfortable for long flights.