I've noticed the draw get tighter as the days go by too!
I'm thinking the screen is down the chimney, ...and the Q-tip is used dry ..and put down the 'chimney' then used to wipe away the gunk? .......Aha! now read on.......
I left the above as I wrote it a short while ago - was just about to say that I've just cleaned a coil by rinsing it & soaking in mild soapy warm water for a couple of hours, then soaking it in vodka overnight and then rinsing thoroughly in clean warm running water. I set it down in a stand a few hours ago to dry out properly for when I want to change my current coil.
So, I got a Q-tip ..couldn't even see anything down the chimney, but oh my word! Looked like black oil or soot on the end of it after a swirl around! After a few more swirls I can actually see that silver toned mesh clearly!
I'm really surprised that all that running warm water, soaking and vodka didn't move it! I could actually see through the side holes that the lining material was white again too.
Now I've tried doing that with the one I'm using! I have found that the gunk came off the rinsed & soaked one easier, and left it totally bright metal. The one I'm using hasn't come quite as clean so easily, but the draw is improved and the liquid tastes much better.
So yes, this is good to prolong the life of the coil, but also very good for extra cleaning after soaking!
Thanks for passing that on

Remains to be seen how the 'washed' one performs ...perhaps in a day or two I'll find out.