At under $20.00 for a replacement its a good idea to simply change them this time of year before hunting season every year if you shoot regularly...
For those that dont shoot all winter or regularly... inspect the hole where the arrow rests...is it perfectally circular or is it oval..if oval replace it ...this is due to arrows porphosing or fishtailing, are the bristles looking in good shape, if bristles are broken where vanes contact biscuit...replace it...it way over due...
I came up with a really good test, even when the biscuit looks like new it can be weakened by an untuned or unmatched bow and arrows that porphoise or fishtail...
I have an 10" pice of an standard carbon arrow that I cut off a damaged arrow and have two different nocks on either side, i use this for a lot of things including loop adjustments and sizing nock points, and to inspect WB
Nock the 10 inch arrow tool and set in Wb as normal arrow, now grab the arrow tool in front of biscuit and with firm pressure make a circular motion inside the hole ...dont force it just firm pressure...if you arrows are leaving the WB with an issue you will find that it gets weakened in that arrow and the arrow tool will slide easier in that spot that anywhere in the hole...if it slides into the bristles with little pressure anywhere, [except the QS opening of course] replace it..
JMHO
Neil