I just open mine up and use a small vacuum (its a pressure pack sized one) on it, every couple of months. All my fans are set to blow air OUT of the box as well, which helps stop dust. I have 4 fans, two on top, one on side, and one on front). A lot of commercial setups, the fans are set to suck air in..(supposedly to cool the unit), and in goes the dust. By setting them up to blow air out, they blow the hot air out of the box, and reduce dust build up as well. At 5GHz, mine runs CPU and RAM around 28-30 degrees (water cooling helps there).
Inside my box. the two blue fans are the RAM coolers, to the left of that is the watercooler over the CPU.
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