Bitly links never expire. If you use a custom domain to shorten your links they will continue to work as long as your DNS is still pointing at Bitly and the custom domain is attached to a Bitly account. While you can hide links and their analytics from the analytics view, the data will remain in Bitly.

Do shortened links expire?

Currently, it is not possible to set an expiration date for a shortened link, but if your account is associated to your Short URL, you will be able to delete or deactivate (pause) the Short URL if you want.

Does Bitly reuse links?

No. Each link Bitly issues is unique and will not be re-used, so you can be confident that the link will always direct to the same long URL is was originally saved to.