I've gone as long as 100,000 miles with no problems. Just clean and re-oil and it's good for another 100,000. On my 89 vert I'm up to 240,000 with the same filter.
There's to much cleaning going on here with the K&N.
Right from their website.
The dirt particles collected on the surface of a K&N element have little effect on air flow during much of its service life because there are no small holes to clog. Particles are stopped by layers of crisscrossed cotton fibers and held in suspension by the oil. As the filter begins to collect debris, an additional form of filter action begins to take place because air must first pass through the dirt particles trapped on the surface. That means a K&N air filter continues to exhibit high air flow throughout the life of the filter while it is accumulating dirt. At the same time, the air flow for an average paper air filter can decrease dramatically as the paper element gets dirty. So as dirt accumulates, the performance advantages of a K&N air filter can increase! Tests performed by an independent laboratory commonly known as the Frazier Permeability Test have shown that the Medium used in K&N air filters flows more than 300% more air than paper air filter medium when compared on a square inch per square inch basis. A Square inch comparison is not directly proportional to the increase you can expect from installing a K&N air filter in replacement of a paper air filter due to the effect of such things as filter size, number and depth of pleats. However, you can be assured a K&N air filter will provide dramatically more air flow which can enhance engine performance.
20. How do I know when to clean the filter?
The general rule of thumb is that the filter needs to be cleaned when the dirt build up gets as thick as the wire mesh. The usual interval is 30,000 - 50,000 miles depending on driving conditions. We recommend that you check your filter about once a year in normal usage