[itsm] How to hide invalid items?

Hi, I am now introducing otrs:itsm in my company. I realized, that some items cannot be deleted, that's fine especially if we speak about audit requirements. But what we definetly would need is to hide the invalid items. Since the infrastucture is considerable and it is quite fluctuating, we have thousands of very disturbing "junk" items. Is there a possibility to hide theese items? Like a flag or something? Above this it would make sense to have a "clean" function, for deleteing everything older than 3/5/7 etc. years. There is also an obligation the remove "expired" items, which we cannot fulfill for the moment. thanks proycon