Damage to skis

wat up fools, i'm drew, new to the site and i'm from kansas, yeeehaw!

i've been skiing since third grade and park riding for the last year and finally getting serious about it. i learned 180s and 360s in my second week in the park and boxes, working on rails now, and think i'll get it all the next time out.

my question is i bought a used pair of k2 public enemies, 169, last years models. how much damage do rails and boxes and that stuff do to the skis. i get to ski like 10 times a year, and think i'm pretty good for what i got to work with. i know it's kind of a broad question, but how long will these skis last? what should i look for in damage and such? just trying to figure it all out.

thanks.