I do believe
the thread's originator is supposed to ask the webmaster for a 'sticky' if there is good reason to keep the thread around past its time, as opposed to 'bump'.
Still, I have seen folks bump stuff here and it never offended me, do it myself occasionally when it's of value...
Some sites are going to a system of + or - whereby threads can be hidden, depending on their level of positive or negative comments. Sure be a good idea around here some times...I wish the instructions on how to fix a Telechron were permanently available...some other threads, well, at least they eventually die.