I am just about to cross 600,000 miles on BMW twins and I have never lubed a spline for its own sake.
My R80 had 92k miles from new when I sold it (stupid move).
My R90S has 62k showing on the odo, 44k of that is mine.
My '94 R1100RS (beta bike!) has 217k miles on it. Admittedly, it has had several trannies, but not because of splines. I put 110k on one, and the current one has 67k.
My current R65 has 173k miles on it (but only the last 4k are mine). However, if I believe the records that my friend gave me with the bike, the splines haven't been lubed in 100k.
I do have a tube of Honda Moly 60 paste, and that is what I put on trans splines when I assemble a bike, but then I don't worry about it again.
Maybe I'll be posting here at some later date that the splines went away on some bike, but so far I have had a 30+ year career without trouble.