Dropbox allows you to create a link to share and set an expiration for your shared link that you create. If you are a Dropbox pro or Dropbox for Business user, then you can set an expiration. You can set 7 days, 30 days or specify a custom date to your link. The shared link will expire at the end of the day you choose and it is based on your time zone. If your link is expired, then you can create a completely new link if you want to share the file or folder again.