I don't think there is any downside to cleaning the air filter frequently when driving in dusty conditions. But more to your question, I find when I drive 75-100 miles on dusty dirt roads alone, with little if any other traffic, I start to lose some performance. Dust is dust and clogs any filter quickly. I'm sure I could let it go for 500 miles of dusty roads, but there is no need - she runs better and its better for it when I clean it frequently. I haven't done it yet, but I've read of some folks carrying a clean filter with them in a zip-lock so they can change out the filter in the midst of a dusty day or two. That sounds like a great idea and I plan on ordering a second foam filter for next year's adventures.