If there is still stuff left to scratch on I would leave it
alone and just rub catnip on it from time to time then
replace it when it is really shredded. They like it torn
up. I think the fraying is only worrying you. ;)

I've seen posts completely frizzled before people replace them. Mine get
slight wear as Pearl aside (she loves to really tear into them) Sugar and
Grant are "light" clawers. If you see anything that might cause trouble if
ingested, cut it off. Otherwise, it's your call when it is "worn out".

The more worn the better - as long as the post is sturdy and doesn't wobble.

Here's and excerpt about old and tattered scratching posts by  Dr. Nicholas
Dodman, Professor of Behavioral Pharmacology and Director of the Behavior
Clinic at Tufts University School of Veterinary Medicine:

"Many owners change a scratching post when it is old and tattered. This is
dead wrong, as shredding indicate frequent use and that is exactly what you
want. Half the fun cats experience from a scratching post derives from
getting their claws stuck in the material and leaving wispy threads as
testimony of their erstwhile presence. More than one post is usually
preferred, perhaps one for each high-traffic area of the house. Different
kinds of scratching posts will provide different challenges, so owners can
profitably get quite creative. A large log (with bark) is apparently lots of
fun and especially good for those conditioning functions. "

You can read the entire article here:

http://maxshouse.com/understanding_scratching.htm

I have 14 posts, trees and condos - not counting turbo scratchers and wedge
cardboard scratchers for my five fabulous female felines that all look like
hell but my cats love them - that's what's important to me.  The only time
I'll throw one out is when it actually falls apart.

Buy another post but keep the old one - your cats will be much happier.

Good luck.

Phil

You named your scratching post. That's sweet.

A scratching post is worn out when your cat wears the pole right
through such that the top half falls over and beans said cat on the
noggin. At that point you get a new post and cat.

But! A serious comment - if you have a sisal or carpeted post, when
these get very eroded, the staples that hold the sisal / carpet to the
post can become exposed. Probably worth keeping a watch and pulling
the exposed staples as needed.

Steve.