I see they give you a few more miles for the Venture. But it is not warranty. More of a maintenance item. They often need no adjustment just checked, so some, like me, stretch it out some. If there does not seem to be a problem.
It is a time consuming job to take gas tank and all the covers off. So it is not cheap. On my Liner it is near $300. Varies some from model to model. your Royal Star has more covers and more valves. A tune up is not much more money. I'm sure if you call your dealer can give you an estimate over the phone.