Mine started making noise at 7K and I recent tightened up a bit.  It helped at first, but not for long.  I think it is in the rocker arm.  Perhaps one of the seasoned guys here can offer more insight.

A look at the adjuster will explain it all.. It looks like its been thru a pencil sharpener, Early on the banging pounds the pint down. It work hardens & spreads out, so, pressure is exerted on more area AND that area hardens at the same time,, SO, initially it will need more attention, as miles build up, less. I sold mine @ 20,000 miles & it was surely over 5,000 since last valve adjust.. It wasnt acting like it was in need at all,,

I like to set mine on the tite side of the specs. It opens the valve just that much more and it leaves it taking longer till its sloppy again,,

Manufacturing or material may have changed. My 05 needed serviced right on that 5K mark, then a little later, then a little later,,I may have futzed with it about 20K,, not sure, I just remember noticing the tips flatten & the time between clacky valves increasing,

Absolutely natural. Those tips work like a woodpeckers face, driving almost straight down, with the only "sideways" motion being the radius of the arc of the lifter as it presses the valve down.. a whopping less than 1/8th inch track it leaves.. Its all good,,