Don't let the math confuse you....
What IF the Honda R&D folks may have done their math so the rear tire(s) would be changed at approximately 10,000 times, so the splines were cleaned and the correct moly paste were re-applied etc.
It would be a shame to find out your math of 20k miles for $100 dollars, turned into needing to replace the rear spline plate and/or driveshaft assembly, from neglect, and not servicing it regularly enough...just something to think about

You may want to consider removing your rear tire half way through, and servicing your splines etc.