Not really, there shouldn't be any loss until you go above at least 160 C (approx. boiling point), which is obviously impossible in a water bath. I have collected the condensed DMT from my vaporizer (I run at 210 C) and used that to enhance leaf. It works great. Heat (not excessive) does not by itself degrade DMT.
Though, I would never heat a recrystalization anyway, because the impurities become more soluble (notice how hot naphtha pulls are yellow). Just give it time to dissolve at room temperature, work it manually to make sure you dissolve all the DMT. As long as you budget at least 30ml of naphtha per gram of impure DMT, you shouldn't need to worry about leaving anything behind.
Don't throw away the yellow goo either. Most likely it is DMT N-oxide that can be reduced to clean white DMT using zinc dust in an acid. I wish I had kept all the yellow goop I've thrown away over the years...