I got stuck whilst trawling though old tweets regarding this year's SAS Global Forum (SGF). I very quickly hit the following message from Twitter: Older tweets are temporarily unavailable. Repeated visits haven't resulted in a different outcome. But I have found a solution.
One of the last messages that's actually available revealed the solution: TwapperKeeper. It's a bit of a strange name but in essence it's an archive for tweets. So, if you visit http://www.twapperkeeper.com/hashtag/sgf10 you'll find an archive of SGF tweets. And you can create your own archives too. Looks useful. Give it a try and let me know...