When you go the a user's profile and click on "find all posts by", you only get her last 100 posts (4 pages). If you want to see older posts, you can try using "search" and go to "advanced search". Enter the user's name and use the search options to find posts for a certain period of time -- like "a month ago" and older. It takes a little more work, but you can find older posts for a particular user. I hope this helps.