I'm glad you plan to stick with it. And yes - it is frustrating that they do not mention the cartos burning. There is a LOT of vaping that i have found to be trial and error.....
In the short term, hopefully you can figure out a technique to get your NPro working. I did find a technique that got decent vapor without burning out the carto you might want to try. Take a quick "primer" puff (1 second or so) just until the light blinks on and then off. Immediately follow with a very slow, long hit (about 5 or 6 seconds). Make sure to suck into your mouth and not directly into your lungs. Also suck very slowly - like sipping through a coffee stirrer. After you have the vapor in your mouth, quickly inhale and exhale. I could get decent vapor and a good throat hit this way. As long as I waited between puffs, I didn't singe the filler. Hope that works for you. Last tip is that the regular cartridges are much sweeter, and I think that some of the burning was the sugar. The menthol seems to have less sugar and doesn't burn as easily. This may also just be my imagination.
In terms of whether to use the singed cartos, that's a health and a money issue. The cartos are kind of expensive at $4 a pop. Ideally, I would not use the singed ones. But I would guess that a singed carto is better than smoking a cancer stick.
In terms of a brand to use, I sort of went all out and got a Joye 510 and a Joye eGo. I felt like I was on to something that was working, so I "went for it". Both have pros and cons. I found youtube videos to be extremely helpful when I was trying to decide. Actually seeing someone use the device somehow helped. There was one video in particular from Ritalee76 that I really liked:
YouTube - E-Cig Comparison
MistressNomad also has GREAT vids that were helpful.
http://www.e-cigarette-forum.com/fo...-videos-newbies-particular-broke-newbies.html
Sorry for the long reply, but one last comment. You basically have to "break" the NPro cartos to see if it is singed inside (you have to pull the cover off, and I don't think it is supposed to come off). If you have a 3 piece unit, you just pop it open and look inside. So no worry about singing the filler.
Again - good luck!
EDIT: Sorry ... one more "last" comment .... I found it difficult to know when to change my carto since it would still produce vapor even though it was "done". As soon as the carto starts to taste funny or burned, change it out. If you continue to use it, it will still produce vapor but it will start to burn the filler. If is starts to suddenly feel "extra dry" in the back of your throat when you hit it, it is definitely done.