lemppari,
Check this out:
it will give a clear explanation how to go about setting your suspension sag,
Conventional wisdom depending on the bike and who you are speaking to suggests your sag should be around 25mm to 45mm or if you know your suspension travel around 30% to 40% of the maximum travel available. These are approximate figures and are definitely not specific to your bike.
The main thing to remember is to do you final sag setting with both you and your pillion + your luggage on the bike so that the sag represents the true riding conditions.
When you go solo you will need a readjust to suit your much lighter weight.
Taking the time to do this correctly and then making rebound and compression adjustments to suit if this applies to your suspension will be well worth the effort.
Keep in mind that if your suspension has already done high mileage then it may be appropriate to have the forks serviced and the rear shock/s rebuilt or replaced if this is not able to be done on your units.
Effective damping is critical to good suspension performance which is more likely to save your life and make your journey safe than spending a fortune on engine performance.
Mark