My Silva lighter's been working for a few years now, although the little element inside that helps make it wind resistant got damaged - my fault. I've refilled it numerous times with from a cheap can of Ronson butane and not taken any special care of it. Seems a lot of you have had problems with yours and I certainly wouldn't recommend it for lighting cigarettes, it's not designed for that - the flame is too powerful and hot - you need something like a Zippo if you're a smoker.
I use mine for lighting fires and sealing rope. I've used it outside in hot weather, cold weather and the rain without any problems. Even so I think that having a Zippo (or cheap disposable) as backup is a good idea if the extra weight isn't an issue. But if you're a non smoker, like me, then you need to make sure the Zippo hasn't dried out since its last use before you take it out with you. Also you need to make sure you don't get the flint wet while you're striking it.