Well I bought my first Mini Maglite when I was 18 going on 19 (December 2005)...I was going on a boating adventure with my friend after mid term exams the next day. I had only started EDCing earlier that year (cheap chinese made led 3AAA models). Before then I did not realize that Maglite was made in the USA. It was on sale at wally world for $7 and something cents. I looked at it and read that it was American made. I made up my mind to buy it and was very satisfied. When I got home, I ditched the Duracells that originally came with it and put in some Rayovac NiMH AA's. I was amazed at the brightness it gave off. I quickly became attached to it. In fact this was the infamous flashlight lost in the sofa during a thunderstorm when I mistook a freight train for a tornado. As far as battery life it was decent, I used 2.5 amp rechargables which lasted forever. Bulb life lasted from December of 2005 until May 2006 (that's pretty good considering it was used every day and over driven on rechargeable batteries). Ironically the bulb burnt when another thunderstorm was threatening. My grandfather said the Cajun French word for "trash". I calmly took the spare bulb from the tailcap and switched the bulbs. Back to normal, not much came of that thunderstorm, but at least I was prepared. What I did not like about this light was, it got switched on and ran down the batteries. It did however give a "warning" of a warmness in my pocket to let me know it was on. Sometimes the tail cap would come unscrewed in my pocket which could be potentially dangerous if the batteries would come out and short circuit. The only other thing I did not like was that it would scratch and gash easily. Other than that, it is a perfect edc if you are on a budget. Plus it takes AA batteries, which are easy to find and affordable. I currently own the Desert Storm incan and the regular black incan...I also have a blue LED and a black LED. Cannot wait to buy the Mini Maglite Pro.
So answering you question; I would say it is pretty reliable, just don't let it get switched on in your pocket and always make sure you have a spare bulb in the tail cap.