The ECtHR has a Q&A for applicants where it suggests that the initial waiting period for an examination of an application is one year. (See highlighted text below.) This may be a goal, rather than a formal rule of the Court.
From:
European Court of Human Rights Questions & Answers
http://www.echr.coe.int/Documents/Questions_Answers_ENG.pdf
What are the main stages in the process?
The Court must first examine whether your application is
admissible. This means that the case must comply with certain
requirements set out in the Convention. If the conditions are
not satisfied, your application will be rejected. If you have made
several complaints, the Court may declare one or more of them
admissible and dismiss the others.
If your application or one of your complaints is declared
inadmissible, that decision is final and cannot be reversed.
If your application or one of your complaints is declared
admissible, the Court will encourage the parties (you and
the State concerned) to reach a friendly settlement. If no
settlement is reached, the Court will consider the application
“on the merits” – that is, it will determine whether or not there
has been a violation of the Convention.
How long will I have to wait?
In view of the current backlog of cases, you may have to wait a
year before the Court can proceed with its initial examination of
your application. Some applications may be treated as urgent
and dealt with as a matter of priority, particularly where the
applicant is said to be in imminent physical danger.