Servers in a data center will run all day and night for three to eight years. Fans will blow an enormous amount of air into the electronic parts. Datacenters are not always dust-free, also small "accidents" can happen from construction works. Over the years the server does not get cleaned so more and more dust can be collected even if it is not that much.
I personally don't have a bad experience with the combination of dust and hardware. The low voltages are likely not enough to cause any malfunctions, even if there is much dust. However, when I think about running a Raspberry Pi 4 with its small PCB including a CSI PCB (for PIKVM) for so many years I am a little bit anxious that it could affect it because it is so small and maybe a little bit more prone to interferences.
My idea is to just use Polyimid (Kapton) tape - simple and effective. As long the Raspberries do not fail, I expect them to last at least eight years, so for one or two server generations. Does this make sense? Or can covering the whole PCB (without the passive heatsinks of course) have negative effects I am not aware of?