Two months ago I had to replace a rebuilt hybrid traction battery in my Gen II that was less than 6 months old because I failed to clean the fan that cools the battery when I replaced it. Luckily the place I got the traction battery from was nice about it. First, let me say they never let the owner replace the battery themselves... that is except for when they made an exception for me. That was their mistake. My hybrid battery went out and I had a long relationship with the battery people. I had bought a battery from them and sold a Gen III battery to them. And the shop is 2 hours away. So I pulled my own battery and met them half way to swap. 6 months later the new battery died. They came out and replaced it. My battery fan was so crusty that it wasn't moving any air so the battery died prematurely. Lesson: Clean your fan that goes to your hybrid battery. It's behind the rear seat on the passenger side. You have to work your way down to it, remove some screws and cut a foam band to get it apart then clean it and put it back together. Just saying.
that seems to be the only time the fan gets clogged. other than that, most only find a light layer of dust boil up. you may want to make a simple pre filter for the intake grille. something that won't impede airflow.