This is such a simple thing that most overlook it, but it's something that no one wants to pay for it when it breaks. Let's face it, $500 can buy groceries for month for a family of 4, 8 very nice nights out, or even a weekend stay in a fairly decent hotel. It can also pay for a month's worth of camping at the KOA (maybe).
What people hate to spend money on is their home comfort system; in my terms, the HVAC system, (Heating Ventilation and Air-Conditioning). The truth is that the price for me to come to your door and find out what's wrong with your HVAC system is about $90 to $130, depending on the time of day or weekend. In addition, the cost of a blower motor installed is $350 to north of a grand for a higher-end variable-speed motor. These aren't cheap, and I've had customers defer these expensive repairs and put up with the sweltering heat and humidity while the equipment they spent good money on sits useless in the mechanical room. While there is Murphy's Law, my stand is that 90 to 95% of these repairs are completely and utterly preventable with a little knowledge and some common sense.
To add more to the carnage, I've seen expensive equipment reduced to scrap metal because of the improper use of furnace filters. Heat exchangers can fail, cooling coils can ice up and cause water damage to circuit boards, blower motors, and other moisture sensitive parts. Did I mention furnace filters? Yes I did.
Neglect is the reason a lot of things fail, whether a relationship or your prized ride and is true for your furnace and air-conditioner chugging happily away in your basement or laundry room. Ignore your spouse, schlep out of doing your oil changes or forget to replace your furnace filter and you'll suffer financially. I've seen filters that were left in "only three months" that ruined motors or resulted in an A/C icing up. The truth is that ANY ONE INCH FILTER MUST BE CHANGED EVERY MONTH YOU USE THE SYSTEM. Even the so-called three month filters will destroy your system faster than the cheaper filters because the tolerances of the material are tighter. Try blowing as hard as you can through one of these filters (before you install it) and you'll likely run out of breath. Then try blowing through a fiberglass filter (one of the blue or white ones without the pleats) and you'll notice the difference. The looser material is easier to blow through for you and your equipment.
Personally, I don't recommend using 1 inch HEPA or "high performance" filters because of the danger to equipment and your wallet. These have tight pleats meant to trap very small particles that also tend to clog quickly. These also make the blower work harder to move the air; costing you more money to heat and cool your home. This is what also shortens the life of your equipment. There is simply not enough surface area to allow enough airflow through these pleats for the blower to work correctly. This is why many media filters are 4 or 5 inches thick to give more surface area and more capacity to trap dust and dirt. A better idea, if you really want to minimize these nasties is to buy an electrostatic filter such as a Trane Clean Effects or American Standard Accu Clean as these will remove the cats and bowling balls and almost all of the smaller stuff. These are pricey, but well worth it and ozone pollution is minimized as opposed to an electronic air cleaner.
If money's tight, there is the option of the 4 inch media filters like Space Gard, Air Bear, General AC-1, Honeywell or the like. These range from easy to change to utterly ridiculous, with the AC-1 taking good manual dexterity to change and the Space Gards without the upgrade kits being a pain in the rumpus as well. I've been installing these for 14 years and they can still be a bit of a nightmare.
If you must use a one inch filter, use a good quality pleated filter with the lowest MERV (the filtering capacity) number you can find (MERV 8 or lower). I like the filters with some sort of cardboard reinforcement to hold the pleats and keep the frames and pleats from snagging on the slot, making them easier to remove or install. To me, this is more important than any supposed filtering ability. 1 inch filters are to keep the cats and bowling balls out of the blower, that's about it. If you're concerned about your health, you're going to have to upgrade to 4 or 5 inch media filter or an electrostatic job. For the "high performance" 1 inchers, you're going to spend $100 to $200 a year if you change these monthly (you'd better) anyway, not to mention a blower motor once a year. Compared to that, $1000 for an AccuClean looks really good. Maranatha!