I'm only familiar with the DMD-07 which like you said, has no heat sink, but like Tankduel (neat website TD, birthday parties and all) says it does have an auto shut off to protect the unit from heat damage, apparently mine has never gotten hot enough, but I bet I've been close, especially when I was in southern Georgia running for at times 1 hour + (at least 5 times).

Calvinwill