I don't have any experience with the 600F, but I do with other recent Hondas.
As the valvetrain wears, do the clearances between cam and follower get bigger or smaller?
On my bikes, valve/seat wear outpaces the cam/lifter wear, and the clearances tighten up.
How likely is it that they need it at [16K]?
While some clearances on my VFR and ST1100 (46K and 26K respectively) are approaching the lower limit, neither has yet required a shim change. I expect that the VFR will require at least one at 48K.
If you have the skill, the tools, and the time, do it. Even if no adjustments are required, you'll know
that clearances are good. And, you'll then have a record starting at 16K so you can anticipate future adjustment requirements.