Alright, I'm not here to troll, but I believe this ought to be said.
I am convinced that cartomizers, when left sitting for a period of time, can accumulate bacteria and/or other undesirable things. I say this because I've caught a vicious cold twice now, and I'm normally pretty resilient to such things. Having used clear cartomizers, I've seen the yuckiness that can accumulate inside. It makes sense that this could be a favorable environment for harboring germs.
If you use cartomizers and like to stretch out their lifespans, protect them with a condom! Or put 'em in the fridge. Or keep the space clean. Furthermore, don't share with others! I'd venture to say someone who's sick would be able to contaminate a cartomizer pretty easily.
Okay, feel free to disagree, but I believe this is a pretty sensible piece of advice.