To expand on Google and tabbed or click to expand content, Google's John Mueller was asked about infinite scroll pages.
The question was at 17 minutes and 48 seconds into the video where he asked will Google index all of the content on your infinite scroll pages.
First, John answers by pointing the webmaster to Google's blog post on handling infinite scroll with Google by using pagination techniques. But John did admit, if there is continuous scrolling forever, Google will eventually stop and not index all of it. He said gigantic pages that scroll down forever, eventually Google will simply stop. So Google may not index all of the content on a page with infinite scroll.
He does recommend you paginate the page either by category or page numbers.
What is the magic number of MB per page? Maybe 50MB but he isn't 100% sure on that.
Here is the video:
Forum discussion at Google+.
