So far a touch over 700 acres on the air filter since we put the pre-cleaner on our CX, it's starting to get dirty but it has been running in some horrendously dusty conditions, I guess with all the rain everything is rotting and covered in mold and mildew. Before this change I would guess we would be changing a filter a day in these conditions. I think if we had gone with something with a scavenging tube it would help even more. Overall I am quite happy, only regret is we didn't do it the first year we got it. I can't believe how many people are having the same issues. There has been quite a few people just on here that have had to do this, and this is only a very small percentage of farms running these machines.