I do often wonder why some rides need retracking like this, and other, much older rides (Goldrusher and Viper at SFMM, Matterhorn at Disney, etc.) don't. I get number of cycles and intensity may have something to do with it, but I'd imagine a ride built in the 70's and essentially continuously operated (thinking about Goldrusher and Viper specifically here) has never had extensive track replacement despite being 30-40+ years old.