If I recall correctly in Mass Spectrometry you can have fragments of the side chain (containing the Dimethyl-Amine) and thus at high energy might be possible that this also takes place in non-MS-environments.
Biggest threat might be quaternary ammonia salts as they have a close resemblance to acetyl cholin, that's why there is a bunch of these (N-)quaternary tryptamines in certain fungi poisons. But guess you would need quite a high temperature, like smoking DMT in a cigarette to make wild cross alkylations happening like this.
Still there is really no reason to ever smoke DMT past 200 °C, as it just vaporizes perfectly at 160 - 200 °C if given enough airflow. As long as this temperature is hit then anything you need to do is getting air flow pretty strong to ensure your spice not sitting too long in a concentrated spot, which will cause this caramelizing dark reaction, making it impossible to vaporize further or dissolve. So as higher temperature only makes this unwanted process faster it's best to focus on strong airflow and a temp at 160 - 200 °C.
Differential Scanning Calorimetry takes track of reactions occuring upon increased heating. The data for DMT can be seen
here. If the curve is strongly spiking it indicates a heat transition, possibly due to a reaction.
As you see:
At T = 230 °C
and
At T > 260 °C
something is happening. That could be the first sign of thermal degradation, not necessarily what you mean but some kind of combustion (even though that would be more likely a curve going downwards, which indicates exotherm reactions.). Therefore: Any heat above 200 °C will not help and only makes things worse. We should all move from open-flame setups to something more precise
