For a long time, I had a terrible Heating & A/C habit, i decided to curb this habit when I discovered how harmful it could be, however the terrible habit I had was letting the air filter go for too long without changing it, however sometimes, I would take a look at the air filter & decide that it was still good, despite the fact that it was quite dirty. I have a tendency to try & get the most out of everything I use, so periodically, I continue to use things that I should just throw away. I have that problem with tennis shoes, cars, & furniture, to name a few things… Well, I can tell you that it is not helpful to become overly connected to air filters that have given up the ghost, so to speak. Such air filters should be relieved of their duties by fresh, clean ones every few months, then however, I will confess that periodically, I just completely forget about the air filter altogether! It took deliberate marking on my quarterly planner as to when I installed the fresh air filter & when it was time to upgrade it. What drove me to beginning documenting when it was time to change my air filter is my discovery that not changing the air filter of an Heating & A/C system, far from being only mildly destructive, can be the root of just about every kind of heating & a/c problem that you can imagine! Simply neglecting to change the air filter could kill the life of your component & cause you to have to make all sorts of costly repairs that could have been actually avoided by a few seconds of toil every few months!