Manufacturers offer replacement parts for vehicles for at least 10 years and normally much longer than that. We can still get Ducati parts for bikes way back to the early 1990's. Over time, after I'd say 15 years or so, some individual parts may be phased out if the back-end supplier of that part is no longer producing it, but it's not something to be concerned about generally unless you're dealing with "vintage" bikes that are 20+ years old. Also, as manufacturer support phases out after a long time, normally the aftermarket steps in and starts to offer alternate options. We work on 20+ year old Ducatis in our shop all the time and parts availability is not a common problem.