Generally content from new terms will begin to arrive within minutes.
Once the initial connection has been made, (you will see the message 'preparing...' in the Last Ingestion Attempt column in Discover > Terms) you can expect the following wait times:
Twitter: New tweets should arrive almost instantly but may take 1-2 minutes.
Facebook, Google+, YouTube, Flickr, Instagram, Pinterest, Tumblr, ECal: New content may take up to a few minutes to arrive.
RSS: This depends on the poll frequency you have selected.