I've been trying to find some type of info on this, but haven't found anything that really helps .... but I'm sure it's here somewhere, just can't find it.

When working with WFxF and WFxF/S lines, in the 5-8 weight range, how much of the fly line can be trimmed, on the tip end, of the fly line before it should be replaced? Is there a "rule of thumb" or standard on this?

Thx's
Mike