I wouldn't be too pedantic about keeping everything "just in case". In the event I get a new bike, if it's a Rocket I'll just swap things like intake and exhaust over so I'd be selling my '09 with some parts off a brand new bike. If it's not going to be a Rocket then what do I need them for? I have kept a set of triples and cut claw because noones getting my intake. If I don't have a bike to put it on, it's going on the wall, with a plaque. Stock exhaust could come in handy I guess if I still gave the bike in 2019 and need to pass a decibel test each year.