Sometimes it depends on the bike, for example my Y15ZR V1. I keep the old cable because it still able to lengthen more by adjusting the barrel adjuster near throttle body, and the throttle grip. But it is the best for you to just buy new one that has more length, then adjust it later.
Is bn thinking about ordering one. Where did you purchase yours...?? And since you've had it what do you think of it after a few months...?? Its winter here where I live in America "snow n col" = Sucks... lol. Can't wait to ride Thanks in Advance. P.s. Subbed.