Add quest timers?

What I mean is, only allow a "quest" for an item to be completed once, or give it a timer so that it can only be completed every few weeks. something long to avoid people camping the same bosses...

A good example of camping ruining what was intended is the room full of twinks camping the guy who drops the ncu ring in subway. I don't think that they should be allowed to pick up the same item over and over, or that anyone should have the motivation to make a character exclusively to complete the same quest over and over. it might not be necessary to make all such items unique, but perhaps if they can only complete it once a month, or once every two weeks, it won't be so incredibly camped.