Final answer:
The question about the duration for which unofficial notices can be posted is dependent on an institution's specific policies, which can vary and thus cannot be universally answered without referencing the institution's own regulations or guidelines.
Step-by-step explanation:
The question seems to be related to the rules or policies regarding the posting of unofficial notices within a particular institution or organization. It's not a question that can be universally answered, as policies can differ between establishments. To accurately answer such a question, one would need to refer to the specific institution's policy manual or guidelines. Generally, rules about posting notices are included in an institution's administrative regulations or student handbook. As such, without specific reference material from the relevant institution, it is not possible to provide a correct answer to this question.