I don't even know what to say. I'm blown away by the fact that while I regularly clean my glass pieces as soon as they are slightly gunky, I have not thought much about how much gunk is actually inside of my lungs...
Just buy one. It is worth it to get a glimpse of the nasty stuff that gets trapped in the tiny carbon filter, even if you don't keep up with it. I do not know the science of how well they work, or for how long they should be used before changing, but I will say I think I am already coughing a lot less in the last week I've owned my MouthPeace. I'm now motivated to look into more smokeless ways to consume my medicine to give these lungs a break!