The guy at my shop said the same thing. As long as those things were fine, he said he'd wait until I brought it in at 26K. He said he almost never sees it needed at 15K. When I took it in at 26K I think 4 needed adjusted but were just right on the edge of even needing it.
Each bike is bound to be different, even though they are the same model. Different riding patterns, different riding styles, different loads, different weather, different manufacturing variances, different oil & intervals, different filters, etc. We are all looking for some type of trend, based on feedback from others. Unfortunately, it is not very scientific this way because we probably don't have enough data and/or don't have verified data and/or don't have it all adjusted for various factors. That said, the only non-scientific conclusions I can draw are from everything I have read (on the forums) regarding valve lash check/adjustment:
Generally, it is rare that the valves are out of spec and common for them to be in spec.
Generally, when there are some out of spec, they are usually barely out of spec and the number of out-of-spec (of the 16) are few.
We know for a fact that the US service interval is much shorter than for the rest of the world, which makes it more political and/or regulatory than actually necessary. The C14's in the US are no different than elsewhere.
Generally, it seems the US service interval is too aggressive.
Generalizations aside, it is very possible for any particular bike to be out of spec after OR before the recommended service intervals.
Running while out of spec can cause expensive damage. The longer and the more out of spec, the more like damage is and the more severe it could become.
It is possible to be out of spec and not know it from engine sound or running or performance, although sometimes one can tell.
As for spark plugs, it seems almost universally accepted that the recommended service intervals are ludicrous. EVERY posting I have read said the plugs were fine when examined, no matter what the interval has been. Verbally, I was told by a service tech that replacement is advised to prevent them from seizing in the head, later causing them to break later when removed, which makes a big mess. I tend to dismiss this (if anti-seize was used properly, that problem should be exceptionally rare).