they will still do the same thing as before. as long as they dont have a lot of miles on them they should be fine. i put a set of rockers on my car that had about 2k miles on them and they were fine.
APPARENTLY over time the aluminum ones can crack and really bend bad so they wont provide as much lift. But I havent seen it yet. The steel ones are supposed to be heavier but better because they will flex rather than bend/crack.
oh yea, when i said aluminum i mean like the blue billet aluminum, im not sure about alloy.