Another thing I've discovered about these Prince coils (this pertains to the Q4 & X6 mainly as the T10 holes are too small for a Q-tip) and, I think it may increase their life, is that after a few tankfuls, I started using a Q-tip to gently wipe off the built up gunk off the coil.
After doing this, I found that it really improves the flavor and removed any hint of 'burnt' taste. You can do this without having to take the tank apart or even take off drip tip. I just started doing this, I'll report back if I find it truly extends the life of the coils.