I use a torch on all my TRWW vapes. I've noticed that most users who overheat the quartz caps typically just brace for impact, pull hard, and end up with a ruined, combusted bowl they have to scrub out. The trick is to treat the cap as a removable thermal battery. Once you sense that you're approaching combustion , remove the cap (the source of heat) and continue to hit the bowl as it cools down. Replace the cap and keep on keeping on.
I currently have eight (8) quartz dome heaters from my variety of TRWW vapes. Right now they are lined up on my Nugbuddy silicon mat, but any jostle sends them tumbling down like bowling pins. Looking for a safe way to keep them while still granting easy access. I find myself (happily) surrounded by glass.
Apparently the number is pretty small. Like 1 to 3%.
To completely eliminate combustion and use only dry herb vaporization requires a deliberate lifestyle choice, a bit of a learning curve, and an investment in dedicated hardware. According to the stats, apparently most aren't prepared to do that. Where do you stand?