With my Ti Woody I've noticed that it is possible to create alot of heat under the right circumstances and I can feel the heat on my lips believe it or not. It happens sometimes when plugging the carb hole for the entire hit and drawing hard, with no downtime between heating cycles. I think what you're saying is the heat created by these circumstances originates inside the vapor path, but will conduct to the outside of the condenser tube where it contacts the O-ring, theoretically causing the ring to offgas, which would then travel back to the condenser input and into your mouth as you're drawing, right? And same deal with the O-rings on the tip?
I would like to think that the hi-temp rings Dynavap uses are rated high enough to withstand that brief heat, but also I was going to say that this is not a regular occurrence for me. It only happens when I'm trying too hard to milk it and it really only happens with whole nugs or large pieces of herb in a partially filled chamber. This is one of the reasons I prefer to use a medium to fine grind, tamped down, chamber 100% full. Finely ground material tightly packed makes vapor production and "milking" more effortless than with whole nugs, and I don't heat up the unit nearly as much, nowhere near the point where I feel it on my lips.. When loading my chamber like that I never feel the heat; the vapor has already been createdand is hitting my throat like a wall before the unit has a chance to heat up to those supposedly unsafe levels.
http://fuckcombustion.com/threads/dynavap-vapcap.18853/page-574#post-1111978