You do need to keep trimming off the end of the quill as it wears down. It's the same as when you use the quill as a writing instrument, not that anyone does these days. Slice the end at an angle, so that there's a point on the downward tip. If you want to be really traditional, you can make the slice with your wee pen knife, since wee pen knives were designed expressly for the purpose of trimming quills.

--Charlie Baum