they should be fine since buttering isn't to hard on gear..
it sounds like you do not ski to hard, so you should be fine. The person who said STH 12 will break at his weight, I am about 160lbs and I have skied 912 914 and STH 12 very hard and they all did fine. That includes park(jumps especially, some pipe and rails) and plenty of cliffs. I would rather have the Tyrolias I am putting on my new skis now, but STH series and 9 series shouldn't break from a 160lb guy. the TI is another story though, they are not good for hard skiers.