I have done this ( twice now )
The first one was years ago when I rode to Aberdeen and back.. Left at 9 am and got back home about 4 am the next day.. Stopping for fuel was enough of a break to wake me up again.. but that was on a CX500.
More recently I did the Italy to home thing in one hit.
The only time I struggled was about 3 AM .. but it was bloody cold by that time and that fended off the sand man
Here is a thought Andy.. ( and it could be why I succeeded )
I had given up the fags a few weeks before.. I still had a certain amount of , not so much craving, but just wanting a smoke every now and then..
It might just sharpen you up a bit ( read keep you edgy ) if you do not have a fag for the entire run.. Just a thought ( and proly a daft one ! )