This is my experience. It lasts a long time and remains playable. I recently had to cut a guy/poly hybrid out of my TC95 18x20, but it's only because I strung a poly known for quick and drastic tension loss too low in the crosses. My son hits the same hybrid in a MG Radical at 55/52, and it's optimally playable at this point with the gut fraying but going strong. Durability is less an issue than finding the right poly cross and tension imo.... My point being that gut/poly in an 18x20 lasts a long time in terms of durability and playability.