Be aware that we (this forum) had an early rooter that decided to run his phone overclocked with the min CPU speed equal to the max CPU speed.
His phone only lasted about a week before it died completely.
Bottom line is that these phones don't have a thermal design which supports things like a pegged CDMA radio, a pegged WiFi radio, and an overclocked CPU all running simultaneously.
High temperatures accelerate many different failure mechanisms; that's one of the reasons that overclockers in the PC space add things like pumped water-cooled heat sink systems and high-speed blower fans - so they get rid of heat before it destroys their hardware.
There's no fan inside your phone - and it's encased in materials with horrible thermal conductivity (plastics & glass). The battery has a fair bit of mass (and thus some heat capacity) - but the mobo in the phone is not in good thermal contact with the battery. All of which combined makes it easy for the chips on the mobo to reach extremely high temperatures.
I would be cautious of using it in a tethering mode for things like streaming video/audio for client stations - continuous power dissipation. If I was forced to do that, I'd take the back cover off, strap it to a heat sink, and blow a fan across the heat sink. (For incidental use, though, I wouldn't go to that trouble.)
eu1