I have one foursevens quark (tactical QT2L-X) on my rifle that sees ~500 rounds a month and plenty of other abuse and my EDC Quark is a tool and it's treated as such, no pampering and very little care, it's been threw more than most people will ever do to their lights (and it wears the scars proudly) and neither have ever gave me so much as a faint flicker, they work exactly as intended, the tactical UI one has never forgot its programming threw >5k rounds down range . Eagletac and O-light (who are both related to Foursevens) are two other brands that I have 100% confidence in. Not saying anything negative about surefire, again I'm an avid collector and love everything they make (lights and all the "other stuff" too), but there is no reason not to trust one of the other leading brands just as much as surefire. Now I'm not saying replace your surefires with solarforce stuff, but there are plenty of other extremely high quality lights out there that can offer 100% dead nuts reliable service, BETTER performance- in terms of light output and regulation (run-time), and a just as good if not better warranty and do that at 1/2 or less the price.
Again I'm not saying some no-name budget light off eBay branded as "cree"> surefires, you have to be smart about it, but there several US based brands that mfg'd in china that have good enough QC that you absolute can trust your life to their lights and foursevens is one of them and I do trust my and my families life to multiple of their products (the one I EDC and more importantly the one on my HD carbine). I also equipped my wife with a single light (an Olight S15) so obviously since I don't have her carry a backup I must have pretty high confidence in it.