How to tell when to replace a filter?

[spahopeful]

I rotate 2 sets of filters in my 2006 J385.  One set is the original set.  Once the sets are cleaned and dryed, they still seem to be OK.  How do I know when I dispose of my oldest set and quit trying to clean and dry it?

[wmccall]

In 6 years, I don't think I have heard that questions asked. It probably was, but good question.  I toss mine when I can no longer get them white.  Obvious holes in them might be a sign, I've never had that.