The old FAA AC20-7N ( its been chnged to something else now) stated engine hose replacement at 5 years. Certainly this was intended for GA aircraft that flew alot, and used H8794 Mil Spec hose (303/111). Aeroquip and Stratoflex made 601/701 and 156 to use a new version liner with a stainless braid to get more life out of the hoses. Great idea,---opps forgot to tell the fuel companies that were using some supposedly different additives.
We've all seen 'rubber' style hoses have issues. H8794 hoses have a 'rubber' (ok a catch-all term for various liners NOT teflon, like rubber, EPDM, Buna-neoprene, AQP, etc) liner, a nylon reinforcement, a STEEL wire reinforcement, and a cotton outer cover. Well most of you may have tried to flex a hose thats been installed a long time and heard the infamous 'snap, crackle, pop' noises. The cotton cover traps moisure against the steel reinforment wire and it RUSTS OUT. So combine that with a fuel or other fluid that erodes the liner and creates a fracture or a void, and eventually it will leak. Without a good reinforcement, its going to get worse, and eventually could be bad.
Stainless braid 'rubber' is better from a flexibility or integrity standpoint, but the liner is still suceptable to the chemicals in the fluids. (I posted a test hose in another thread that was supposely on a flying aircraft that leaked through the liner.) Teflon is inert to virtually all chemicals in use today. Industrial, bio medical, aerospace, it just works. Higher fluid tempurature capability, higher external temp capability even without firesleeve, generally a higher working pressure are just a few of the attributes. Replace them generally once for the lifetime of your aircraft.
Teflon assemblies DO take some care when removing and reinstalling them. YES---inspect them, especially if they have made contact with structure, or some other object. BUT---generally speaking, teflon assemblies will last the lifetime of your aircraft.
Tom