The standard on all SE sites, unless they request otherwise, is that single-use tags are deleted after 6 months. There are some sites that have this disabled, particularly those which tend to have a lot of low-use tags.
That's exactly the category we fall in to, with over half of our titles as single-use. These aren't necessarily bad tags; most are about a particular series, and there's not much else they could be tagged with besides the series tag. Those tags will get deleted, and the questions will become tagged as untagged in most cases.
Should we keep this auto-deletion script on, or request for it to be disabled on our site?
Note: This question is intended as a poll; please upvote the answer you agree with, but do not downvote the other one. If you have more to add to the discussion, feel free to write your own answer.