A good set of brushes is so essential to a good makeup application, and if you take proper care of them they can last you for a decade or longer. My favorite indestructible brushes, both from my personal stash and for professional use, were made by Bdellium Tools, Royal Langnickel, and Shu Uemura. Obviously, I have invested a great chunk of money into making sure that I have the proper brush for every job, so I am meticulous about their care. Bad things happen when excess moisture stays in the brush. At best, it can get in the ferrule, weaken the glue, the hairs begin to shed, and your 65 dollar brush is now just a stick. What's the worst that can happen? The combination of excess moisture, haphazard cleaning, and improper drying or storage can lead to spreading of germs and bacteria to yourself or your clients.
I clean each brush individually, disinfect it, squeeze out the excess moisture, and lay them flat to dry. My Inreda Makeup Brush Drying Mat (because that's what it is) is 3/4" deep, which elevates my tools away from whatever hidden bacteria may be lurking on surfaces, allows for air to completely circulate around and through the bristles, and gets the brushes dry faster. Do you feel the need to sanitize your fancy new drying surface? Spray it down with alcohol or pop it in the dishwasher.
The Inreda DVD rack costs seven dollars in the media storage area of Ikea, so I bought two when I thought that I would use them to organize video games and DVDs. Laid out side by side, the two mats can evenly dry about 100 brushes at one time.