PROTO.JP has created a script that loads your Tumblr's next page by simply scrolling to the bottom, thus creating a continuous feed effect. Your page navigation is no longer required. You don't have to worry about your Tumblr lagging because it only loads a page at a time (every time you scroll to the bottom).
Copy and paste into your theme box, in between </header> and <body>.CODE
<script type="text/javascript" src="http://proto.jp/js/tumblrAutoPager.js"></script>