Okay, then let's just try this common sense approach: what are you wanting? Are you simply wanting durability and nothing more? If so, then kevlar is for you. I like to call these pick 2 of 3 situations. We have playability, durability and cost. Multifilaments are very playable and typically inexpensive, but don't last. NG is very playable with better durability than anything but poly and kevlar, but is costly. Kevlar is durable and cheap but with the least playability. Poly is a different kind of the playability and cost analogy, as its durability is defined in terms of hours until death. Kevlar, as I said previously, has the worst tension loss of any string out there. Natural gut has the best. Poly has pretty decent tension stability but then eventually dies. Once it's dead, however, it doesn't get worse. It simply stays bad. Of those three options, which is the one that you are most willing to live with?
In my personal view, if you're playing this often, you're likely trying to improve. If this is the case, kevlar is NOT the string for you as it provides extremely little feedback and encourages using far more muscle than is necessary with any other string type. All of the kevlar converts I string for initially think that all other strings are simply cannons when in fact it's that Kevlar doesn't even have a fuse. Most importantly, which is what phoenix alluded to, is that if you're working on getting better, you NEED consistent strings. Restringing regularly as you're steadily improving is unfortunately part of the sport once you get to a certain level. It's akin to using the same set of balls for 100hrs while honing your strokes.