Yeah I cleaned mine two weeks ago and i have had a few k&n's so im familiar with how liberal you have to be with the oil. I always think I am going to forget that sensor but I dont. Fears of old habbits I suppose.
I believe K&N has a million mile warranty(or they used to) as long as you clean and oil it like you are supposed to.I ordered a spare during the Black Friday sale. These filters look very much like something from K&N Filters, which means that they should be able to go something like 50,000 miles and still filter air better and flow better than stock paper filters.