Do you clean the teeth before filing?
I have the oil always on max, and sometimes the chain is oily after use.
Small wire brush and a drop of break cleaner or wd40. Big difference.
Another thing, i got good at grinding the depth limiters with a worn flap disc.
Fast and close to spec.
How many chains can you sharpen with one file? I mean until the teeth are at limit. I could do little over 2 15"64 dl ,325" with some machine sharpening.
Now i know what a PITA it is to run a dull file, i have a stash now.