2.7 RS cylinder wall coating longevity

[RayM]

This is my first post on this site. I've been reading the great information here for a while. Just want to preface my question with my condolences to black beauty and Jack, at least I got to view your car up close at the Ventura show. My question is how long does the nickisil coating (allows for larger bore by reducing friction) on the cylinder walls of the 2.7 RS last? Does it need to be recoated. I'm considering the purchase of a replica consisting of a 73 911T body with a RS motor, mileage unknown, never rebuilt, only thing added was a chain tensioner. I'm also apprehensive about the usual 2.7 stuff valve guides and studs (read past discussions). Thanks for any advice out there.