To read more than 20 tweets on Twitter, you can click on the MORE button, change the page URL, or use below 2 extensions for Firefox browsers.
1. AutoPager
AutoPager is a Firefox add-on, which will let you read more tweets automatically without clicking on the “more” button.
Besides Twitter, AutoPager is also available for you to read more results from many other websites, such as Google, Yahoo, Bing, and so on.
2. PBTweet+
PBTweet+ is a Greasemonkey script for Firefox, besides reading more tweets, you can also reply to all, view images, watch YouTube videos, and so on.
Besides Firefox, this PBTweet+ extension is also available for Chrome and Opera browser.
By the way, both of these two Firefox extensions are free. 
Related free web apps:
