planning, planning, and more planning.
pick a route, then consider where along that route will be the busiest location, then work your times so that you avoid the busiest location at either rush hour. even if that means starting at what seems a stupid time. consider the direction/location of the sun too.
doing most of it on Aroads, duals and Mways will be physically worse than going by the twisties cos you're just sitting there rather than moving around keeping loose.
take a longer petrol stop every second one otherwise they will all get consecutively longer, you'll stiffen up more and get mentally tired too. but don't take too long cos you'll need to keep your average speed up above 50mph sounds easy, but for every minute stopped you need one at 100mph to average 50 - that's where a satnav can come in handy to keep you ontrack with various ETA's.
consider intercoms to keep each other alert, guide thru traffic etc.
you need to practice a bit and try "Combat Touring" ie ruthless filtering at lights, junctions and roundabouts, being quick of the mark at each and quite willing to (safely) mug other vehilces - the lead bike's intercom helps here if you use clear signals.
LE & Lowestoft - west and east compass points? and why 16 hours?
see
www.roundthebend.org.uk