Are hidden systems being created all the time, or are they static (as in they are all built already and whats here is here)? Cause if its the latter that kinda sucks, cause there's a good chance there all taken. Also if hidden systems are randomly generated, are they destroyed after a while if no one finds them to prevent galaxy clutter? (Newb questions i know, just curious).
Yes and no Ten. It is possible for a system, or collection of planets that are not hidden now to be made hidden later as part of the Galaxy Team's process for making the galaxy more canon. However, there would have to be strong evidence for making such a system. I do know that there have been several created in the last year or so though, so it can and does happen still.