Personal Experience: 
After about a year, espically with adult cats or multiple cats, the cat scratcher becomes pretty worn. There's no need to buy a whole new scratcher, it simply means it is time to replace the rope on your scratcher. 

How to Replace Rope:
1. Take off old rope with scissors
2. Heat up your glue gun
3. Place glue on the post and start wrapping it around the post

There are 3 choices below for you to look at for replacing  the rope on your cats scratching post.

Replacement Rope #1

Amazon Link: https://amzn.to/3OG6eSx

About Product:
Length: Comes in 33, 66 or 164 ft.
Thickness: 6mm (1/4inch)

100% natural hemp rope that has been twisted using ancient methods, dried by hand, and is safe for both people and animals. Because of its strength, the hemp rope does not shed any of the microscopic dust particles that either people or cats breathe into their noses. If the rope is scratched, it simply leaves large, simple-to-clean crumbs on the ground.

Replacement Rope #2

Amazon Link: https://amzn.to/3boAfaR

About Product:
Length: 98 Ft (30m)
Thickness: 5mm

Manufactured with natural jute rope, which is strong, adaptable, and completely safe for your cat.

Replacement Rope #3

Amazon Link: https://amzn.to/3OwFkMG

About Product:
Length:  150 ft
Thickness:  2 Ply

Sisal fibres are used to make natural fibre rope thread. Great strength, endurance, stretchability, and resistance to degradation in saltwater. Able to withstand abrasion and is suitable for severe environments.