Owner of several teralux mini stars - Lightstar MiniStar ST/EX LED Conversion Kit for Streamlight Stinger Flashlight

I have in the past purchase several of these teralux mini star conversions .
I have a question if it could be answered .
I have had two of these stop working . I do not believe that an led burns out.
Sent both units back to light star corp. and of course they were both out of warranty.
So I just wanted to know what and or why these units quit working.
I asked this question to light star corp.
They did not answer or would not answer.
But that being said the unit is a very bright and easy on battery.
like I said I have several in vehicles and in work areas.