Hi Element!
Yes, these coils do wear out, but you can probably get a lot more life out of it. The good news is that they are common, so they are easy to find, and they are cheap, usually under $10 for a 5 pack. With proper maintenance and cleaning, I get about 3 weeks out of a coil before I clean it, and I get between 2-4 cleanings out of a coil. Doing the math gets me about 9 weeks or so conservatively per coil.
Did you clean the coils before swapping flavors? Menthol is a VERY hard flavor to get out of a coil, and if you didn't clean it at all, it is no wonder you are getting horrible flavor. It could also be that you got a juice that just tastes horrible, it is hard to say what the case is here. As for the vapor, it could be the coil, or it could just be the mix used for the juice. Some juices produce more vapor than others. Did it produce better vapor when you changed flavor, or has it been this way since the switch over? I have found that most of the fruit flavor vapes don't give nearly as much throat hit as a menthol or cinnamon vape, but be careful with strong flavors because they can cause your plastic tank to crack. Adjusting the iTaste up may help with the throat hit and vapor, but the flavor will get weaker, so you could try that too, it might fix the bad taste by removing it.
I recommend trying to clean the coil with alcohol and see if that helps anything. Here is the best way that I have found to clean them.
DO NOT USE RUBBING ALCOHOL! I have found that using grain alcohol (Everclear) works best Here is what I do ...
1. Rinse coils under hot water for about 30 seconds, wrap in a paper towel to dry off excess moisture, repeat 2 or 3 times.
2. Place coils in a shot glass.
3. Cover coils with Everclear and allow to soak for at least 12 hours (longer if really gunked up)
4. Remove coils from shot glass, wrap in paper towel to remove excess moisture and allow to dry for about 4 hours. If you can't wait, then dry burn them for about 20 seconds, wait 60 seconds and repeat. Do this as many times as necessary to dry them out.
As for replacing the whole setup, I would recommend giving this one a try for a bit longer first, unless the battery just won't hold a decent charge. What you have is a pretty good setup that should work well once you tune it in to your vaping habits and style.
The iTaste VV is an 800mah battery and should last about 8-10 hours on a charge. It doesn't matter for battery life, but do you know which version of the iTaste it is? If it is just VV it is a version 2 and if it is VV and VW it is a version 3. The easiest way to tell is the color of the numbers on the display, Red is v1 and v2, and Blue is v3. I am a chain vaper too, and my iTastes usually last just about 8 hours each (I have 2 of each of them, 4 altogether).
All of the info here is what works for me, YMMV.