I'm a first hand experience follower of "lube it or lose it". I think many have seen and read my story. My bike only had 13.5K original miles on it when I bought it, but it had been sitting in storage for quite a few years, and likely had never had its plines serviced prior to that. There was absolutely no evidence of remaining grease when I took the bike apart after my friction disk splines and transmission input shaft splines ground themselves down to nubbins, leaving me to push the ol girl 3 miles back home. At least she had the decency to let go before I started down a 2 mile long hill!
If someone is a high-miler each year, maybe one can go for more than 15-20K miles between lubes. But if you're more "average", or if it has been 5 or more years - I'd recommend it to avoid the grease drying out.
The Moly-60 PASTE is good stuff, but I've recently observed that it does dry out much faster than the more liquid, sticky grease. I'm now an advocate of mixing MOLY-60 in with a good sticky grease (Red-N-Tacky at tractor supply, for instance) to get the benefits of both.