hmmmm....thats a tuffy. If this is for your " El Cheapo"...go for it..RRs dont take to much abuse, the do wear a little, but not a HUGE deal. Any other opinions....
It depends on why the previous owner is taking them out. If its because something in the motor went wrong I would stay away. If he just didnt like them or something of the sort then go for it.
iv'e read somewhere the majority of aftermarket roller rocker wear out at about 40k miles. the cobra ones happen to be of a high quality and oe so should have lots of life left on them