I had both my 12v and 18v flashlight bulbs go out quickly on my M series Milw. flashlights.  The reviews all stated that the replacement bulbs went out quickly as well.  I just recieved  these bulbs and tried them out; the first 10 minutes on a freshly charged battery I smelled plastic, and after 1 hour and five minutes I found lens too hot to touch(probably before that time as well).  I only checked it twice as I was also watching a film. I found the reflector to be too hot to touch, and the little paper ring between bulb body and reflector came unglued.  Bulb spring was hot but not too much. No scorched or melted plastic.  Incidentally,  the beam blinded me when I looked directly into it.  I even banged the flashlight around a bit and didn't lose the bulb.  This puppy is going back into the van and back to work.  I may replace the paper ring with a couple of neophrene washers to isolate the bulb/reflector, and I will also definately drill a couple of holes in the botton body to facilitate convection out of the side vent holes, cooling the back of the reflector.  As I am a plumber, I'll not drill holes in the top for water to get in, of course.  This test was with flashlight sitting vertically on bottom of battery with lens set to shine horizantally/90 degrees; usual working position for me.