In case you have missed it, when you scroll down to any of the Tweepi tools pages, you will find a box which asks you to tweet about Tweepi to “unlock the 40 per page for a month”.
When you do this, the display of tweeps per page will automatically change from 20 to 40 for a month. This helps you go through your tweeps faster and more effectively!
Note: If you don’t like the text of the tweet, try closing it and clicking “Tweet” again, it will choose a different message for you. Of course, you can customize the tweet you send about Tweepi as you please :)