When, and how, to suggest merging of questions?

Background

Just today, we had the following situation:

Proving by induction that $n^{n+1} > (n+1)^n$ for $n \ge 3$

Prove by induction that for all $n \geq 3$: $n^{n+1} > (n+1)^n$

Usually, I can see some merit in keeping duplicates for indexing and visibility purposes. But in the above case, it seems very reasonable that (perhaps on some longer term) these questions be merged, because such benefits are absent.

Question

Some search did not reveal any information on:

• What the requirements/guidelines for merging questions are (this includes a time perspective -- how old do we need the questions to be before merging);
• How one can bring merging candidates meeting these requirements to the attention of moderators.

Thoughts and suggestions are appreciated, as well as "official" response.