Crf 250x questions.

I am looking into a crf 250x. I have been told by people that they are good bikes, just that they can be high maintenance. I was told (By a Mechanic) that after any time that i ride it, i should pull the air filter and clean it. He said alot of people dont clean their air filters, so that is why people's valves go south and that is why you see alot of dead bikes, or bikes with new top and bottom ends.

On another topic, is the stock Crf 250x exhaust spark arrested? Thanks,

But on my 2 stroke, i clean the air filter after a handfull of rides. But i can see the fact taht 4 strokes turn over extremely fast, relying on alot of airflow.