Set your static sag to the 25mm(hard) to 35mm(soft) range and then set first the compression damping to coincide but not interfere with the spring and then set the rebound damping to control the spring as it extends. There are no exact figures, clicks, number of turns for accomplishing this, because as you suspect, your rear shock can get softer over time as the oil inside ages.
Static sag should be set with the rider sitting on the seat and set to the hard end of the range if you ride 2-up. And remember, no one suspension set-up works for all different uses. When you ride loaded with luggage and a passenger, the setup you use for riding solo will not really do the job.
* Last updated by: Danno on 3/4/2014 @ 4:15 PM *
'07 CPB Blue; ZGST windscreen with MRA X-screen adjustable spoiler, tube bar adaptor, PC III, ATRE,BMC air filter, modified stock seat with 2nd Look cover,Scorpion Flame Ti slip-ons, Galfer rotors front and rear, braided-stainless lines, C-F 10R front fender, C-F hugger, C-F inner fairing panels, painted foreman's fins with faux C-F inlay, polished rim lips wired for heated gear and accessories, Givi V35 side bags and E41 topcase with SW-Motech qd mounts