Some cases have better air flow than others and won't be a huge concern. On the other other hand, all that dust in the power supply in the fans, etc can and will cause failure.
I have a vacuum cleaner which blows as well as sucks. I blow mine out about every 6 months, or when the fans start to get noisy from accumulated dust.
You're a lucky man gnome! Mine doesn't vacuum, clean, blow, or suck anymore! Sorry, couldn't resist a little Halloween humor