You don't want to use regular grease there. Go to your nearest Honda dealer and get a tube of "Moly 60 Paste". It's about $10 for the tube, but it has a much higher molybdenum concentration and is really the only thing you want to use there because of the high load and heat generated by the splines. Regular grease will not adequately protect the splines.
http://www.chaparral-racing.com/Product/pro-honda-moly-60-paste/19-1063.aspx
I'm not so sure I agree with the above. Yes, the Moly 60 paste is a good premium grease to use.
I used other types of premium grease, not necessarily with a high moly content for the first 100k mi on my bike. Splines on the rear hub look like new, the ones on the shaft look really good. Bike now has 159k miles on it.
I think the fact that the splines get lubed helps a lot, with the moly 60 paste being a superior product to do that with.
Any bike chewing up splines with 30-70k miles would seem to be ill-maintained, but maybe there is another explanation.
BTW, this bike is not babied.