Speaking to the uneven mileage intervals between riders and cam chain wear:
The riders right hand has more of an effect on cam chain wear than oil type or quality or tensioner type or quality.
Lots of "brap-brapping" at stoplights, wheelies, or other sudden "drop the hammer" throttle use is hard on the cam chain.
Some of the responses in this thread skeered me so I checked my CCT notches, I'm at 4 clicks gone and 9800 miles on my '07 SM610.
08 TC450, 07 SM610
93 WXC360, 84 CR250
77 360WR, 76 360CR
a GSXR, a YZ, a couple CBR's
and a couple Harleys