How long before they are actually perished ?. Surely it will depend on how hard you are on the brakes. The fact most people get 24 thou out of the front pads leads me to think this bike is not hard on the brakes.
I don’t know, I’ve never waited that long. I think it’s more an age thing rather than how hard on the brakes you are. Braided lines do give you better brakes too but that’s not the reason to change them..