There is a maintanance schedule in the owners manual and the service manual.
Even though the splints
slide together as if there is no space between them, there is a tremendous amount of space there if one were to look at it from a machinists point of view. Each time you accelerate and decelerate the splines clash together (throttle on, power goes thru the final drive, final drive spins, final drive spines free spin a couple of thousands of an inch until they clash against the wheel splines, wheel splines pick up the power and transfer the power to the wheel. the opposite is true on decceleration). The lubricant, moly 60 in this case, is there to absorb the clash of the two sides of the splines or act as a cushionto prevent metal to metal wear! Should this lubricant wear out ( lose it shear strength) the splines start taking a beating and wear faster than normal. Should the lubricant wash out or dry up over time then the splines will wear faster yet! Considering there is 100hp +/- going to that spline, regular replacement of the moly 60 paste ( see your maintenance schedule) is highy important in his high stress area of shaft drive bikes. Also I'm betting that Sport Touring bikes and the riding riders put them through creates more stress against the splines than the average shaft driven bike. Valkrys also have some issues due to the power of the big 6 engine that scoots them along, though not as often as ST's. In a nut shell, If you intend to keep your ST for 30k plus miles and don't mind spending big bucks for a final drive then not keeping up with the spline maintenance with moly 60 won't be a big deal......
Hope this makes sense.