I've had mine replaced during a routine service check @ 42000 km. I guess that might just be about their normal lifetime, don't worry too much about goofing up.
I'm not sure if replacing throttle cables can be done similarly to replacing clutch cables, but there's a trick with clutch cables - detach the mountings (at the lever and at the engine), tie the new cable's end to the old cable, pull the whole thing through and you end up with the old cable removed and new one sitting in it's place, with correct routing and all. All that's left is to attach the new cable to the mounting points. It might be more difficult with a throttle cable, I don't know.
2015 Versys 650