When coming to post a question, one looks for the most fitting tags.
After a while, it may be apparent that a new tag is in order. Good examples are the elementay-number-theory and elementary-set-theory and so on.
However, sometimes when the topics are of higher level, it might be as apparent (i.e. there is not a substantial amount of questions, and it is doubtful that such amount will ever exist at all).
What should be a good rule of thumb for "when to add a new tag"?
Edit I'm not posting this question in order to advocate against new tags, I'm sincerely wondering when it is appropriate to split an advanced topic into a new tag, especially when knowing there will not be more than a dozen or two questions per year.
Edit 2: (TB) I'm adding to this thread in order to revive it and in order to avoid creating a (possible) duplicate. In the last few hours there were the following new tags:
How should one deal with them? In my opinion they are all way too specific and in order to make them useful one would have to go through many questions that should belong to them and add the tags. Should one delete them unilaterally (i.e. remove them from the question and wait for the engine to burn them) or create a new answer on the Tag merging and synonyms thread?