The risk just isn't worth the small savings for me anymore. A contaminated or clogged filter can affect the booth's airflow, leading to improper paint curing and a host of finish issues. I learned this the hard way on a project where I was going for a specific ash white color combination. The finish ended up with a slight orange peel and a few bits of dirt that I'm convinced came from a filter I'd tried to stretch too far. It was a frustrating lesson that cost me more in sandpaper and repaint than a new filter would have.
