Files are some of My most protected tools. They are cleaned frequently with a file card or wire brush when in use, and are not stored dirty. A spray of WD40 or penetrating oil is often applied for rust prevention.. Files have a cloth to be would up in, or some type of sleeve to avoid contact with other tools. I use a firm, steady motion when using a file, lift on the return stroke, and do not back drag. I never "speed file".
I keep a junker-loaner available for the file-less souls who lack a file or the knowledge to use one properly. The people in this group are the majority..