The dearth of comments on this procedure is testament to how often it is needed.
OK, here is my experience from a sister brick to yours.
My bike has over 114,000 miles and came to me with no service records, but judging from it's condition I'm guessing the valves were never done. I say this because the word on the 4 valve engines is that the valves hold their clearance. Thus, they wouldn't have needed adjustment during the early part of it's life, and I'm pretty darn sure they weren't addressed in the last 50-60,000 miles.
So, assuming they were never done, here is what I found. Out of 8 exhaust valves, all were still in spec, however, several were at the tight end. All the intake valves were in the middle. I could have left them alone, but since I was pulling the head and replacing the valve guide seals I decided to get all the exhaust valves as close to the wide end of the spec as possible. I wound up changing 4 exhaust shims. Had to buy 3.
On the 4 valve engines it's a royal pain in the ass to do the shims, about on a par with changing the clutch o-ring. You need to pull the cams, and the timing chain to change the shims on this engine. On the bright side, at least I was able to get the job done without needing any special tools. Figure at least a day(a long one) start to finish. I was lucky(!?) in that I was able to do it as part of a head reassembly. Still, it's not something I want to do again soon.
My advice is to check them, record the clearances and store them. Unless a valve has totally gone out of spec I would leave everything alone. A complete check should take less than an hour start to finish. If you absolutely have to do them, get a firm quote on having the shims changed from a reputable mechanic. That should convince you that it is a job you might want to learn how to do.
