Tim... been out of town hunting and just saw this thread.
The file I was using and prefer above all others is the Grobet. They last much longer than others at comparable price.
When a file gets to looking "shiny" on the cutting surface it's time to replace it.
Most guys hold on to a file long after it's lost it's real effectiveness... don't be cheap! Put the old one in the tool box for other work if you have to, but a sharp file makes a better edge, quicker.
Glad the video helped my friend.