Don't even think of LD riding with a chain drive M/C unless you want to do a lot of maintenance in route.
Sorry ... This isn't even close to being true!
Accepted, a well set up shaft drive involves less maintenance but ...
A decent chain and sprocket set, with an automatic oiler will go tens of thousands of miles with no more than routine adjustment, which takes minutes.
Additionally, the whole set up can be changed out pretty fast and at modest cost. Shaft drives have their clear advantages, but if they break then, in most cases, you are toast.
Personally, I would choose a shaft drive, but I wouldn't necessarily think that it gave me much of an advantage over a good bike with a decent chain, and a rider who knew how to look after it.
+1 I've had lots of shaft drives and ride a chain-driven DL-650 in addition to an FJR. Maintaining a chain so that it will last 15 or 20,000 miles is not difficult at all. A little more work than changing the lube in a shaft drive, yes - but it is by no means a black and white issue. Final drive issues in BMW bikes have caused many people to reconsider the previously sterling reputation of shaft drive systems and, along with advances in chains and chain lubrication systems and the introduction of some really cool bikes that are chain driven, there's been renewed interest in chain drive among serious long distance riders and rallyists.
You'll see a lot more shaft drives than chains at an endurance riding event, but you can ride long distances (and rally very successfully) with a chain drive bike, no doubt about it.
Ease, quickness and availability of any RD failure repair during the IBR is also an important factor.
I am not a Bimmer pilot but I'd assume that even with Saint Supermeese having a whole replacement rear drive with him, it would still
take an experienced Bimmer mechanic with some substantial tools a lot more time to replace a rear end than it would a chain.
If I had a drive shaft failure myself having the limited mechanical skills that I do, (see tagline) I would much prefer that shaft drive rear end be repaired by a brand knowledgeable mechanic (dealer more than likely) which may or may not be anywhere near where the bike is. On the other hand, if I were carrying a spare chain with me and didn't want to replace it myself, I'd suspect even a lawn mower repair shop could probably actually replace the chain.
It would not be difficult for a failed shaft drive RD to escalate to the point of a Timebar or other DNF of the (approx $10k to run) IBR, probably much less likely the chance of that happening on a chained bike if the rider is carrying a spare chain.
With certain brands the shaft liability is even higher.
There is certainly some degree of angst amongst certain Bimmer riders going on in their head throughout the rally wondering that simply is a non-concern for other brands or even a bike with a spare chain in it's saddlebag. Those riders can worry about other things than
their RD failing and knocking them out of the rally altogether.