The FLASH! Cracker will protect itself from overheating.  It contains a thermal overload protector inside of the small red box where the power cord attaches. 

Note that the FLASH! Cracker pulls about 1.3 amps when charging and if you are running them constantly you could be overloading the device they are plugged into (such as an AC powered motion sensor which typically can only handle a sustained 1/3 of an amp or less).  So the shut down of the FLAH! Cracker may be due to the circuit it is installed to and not the cracker itself.

Use a relay based controller (such as the PicoBoo) and a motion sensor attached to that to help overcome this problem.