It has been going on since last November -- eight months.
I drive about 2,500 miles/month and gas prices here in northern Virginia are now about $1.80 - $1.90 for premium.
I'm very intuitive when it comes to car problems, which is why I bought the air filter on a whim in November, but somehow neglected it until this past weekend when my "sixth sense" shouted at me to take action. I wonder what would have happened if I had not done so?
I should add that the 260E/300E 2.6 is a tough little car, and has faithfully kept going despite occasional neglect or minor system failures.