Fix so that the shaft is in oilbath - they kind of tend to last longer if lubricated...
Yes I know they're not supposed to have oil in them - so what?!
Older beemers had - those shafts lasted.
As for pure service things... depends on when they were performed last...
Concerning your plan 2 years in hard conditions... you will encounter "service situations"... -
I would have the gearbox overhauled - new bearings and low 1st and high 5th also installed.
Maybe it is about time to install new valves and valveguides? Then install valvestem caps at the same time - saves the valve-butts and rockerarms.
Check the finaldrive for play and wear. If suspicious - overhaul now.
Forks - new seals, and install gaitors to protect the forklegs and seals. Use Omega 699 automatic gearoil (5W/20) and Omega 917 seal improver => seals will last the trip less you damage the forks.
I'm a fan of oil-coolers. Install an oilcooler if you do not allready have it.
Check the alternator brushes - if worn; renew now.
Regreas the stearing bearings and swingarmbearings; Omega 77.
If you have conic roller bearings in the wheels - regreas with Omega 77.
Check the wire loome and fill all connections with grease to fight off water and moist that will cause electrical problems if it gets into the connections.
Change bad or worn wires now.
Air-filter - see other thread here. Foam-filer is a good option.
If you choose to use Omega 690 80W/90 GL7 you will not need to change the hypoid during these two years. You may however need to top the final drive and shaft a couple of times. This reducing the needed oil-serevice to engine oil changes. Omega 757 20W/50 will last the two years also, but I would recommend that you change at haft time (or before 20 000km).
Steelspun brakehoses, Spiegel or Goodridge, gives a bit better braking. use Omega 917 in the brakehose fluid - improves braking operation over time considerably.
Bring gas-wire, chocke wire and clutch wire with you - if you leave them at home, they will brake - if you bring them along, they wont brake -
Install fule-line filter - the filter inside the tank does not filter well enough.
I use:
Biltema Sverige
Inexpensive, see through - easy to see when it is time to change.
Oh... clutch... never worn out a clutch on my R80. Friend of mine wears out his clutches at about 60 000km intervall on his R100-sidecar... so,... perhaps you should pull the clutch and measure the frictionplate?... Maybe a new is due?...
Probably forgotten a lot of things, but these that I have listed should at least be the main and most important service issuses.