I always find these dust stories curious, as I don't take any anti-dust precautions with any of my electronics yet they haven't suffered from dust abuse AFAIK. eg. When my old PS3 died and I opened it up, it wasn't full of dust despite a few years in a moderately dusty room.
The HEPA filter idea is an interesting one, but won't you impact airflow with that? That's possibly too fine a filter to be meaningful and you could just use a larger filter size. In my personal experience, it'd be more trouble than it's worth. Then again, maybe dust damage is affected by region? You'll have different types depending on location. Obviously cat hairs as per the OP have a significant choke on airflow, but for smaller particles, I guess location will affect how likely the particles are to adhere to surfaces, penetrate smaller cracks, etc.