DMT doesn't die because it's not a living being as we know it
DMT boiling point at atmospheric pressure is not published anywhere in literature AFAIK. As benz pointed out to me once, some calculations state it will be 320c, but to me this seems very high, maybe too high, but who knows. From my experience comparing using the vaporgenie with a vaporizer with known temperature, DMT seems to combust/break at lower temps than that. If you keep under 100c you're definitely fine.
In any case it seems youre asking about boiling an acqueous solution containing DMT (in salt form, like a mimosa/etc brew), and in that case, you dont have to worry, you can just keep boiling and DMT wont degrade.