It's great when one of your Happy Friends posts a lot of tweets, but it can get unmanageable quickly. So I added a couple of features recently that help manage the flood.
Delete All Tweets, a new command in the Friends menu, is the radical approach. It just starts all your friends over from scratch, deleting every tweet under every friend. I actually like to do this, but then I'm not trying to create an archive of tweets with Happy Friends.
A more nuanced approach uses a new Happy Friends setting that groups all tweets under a sub-heading for the day. Turn the feature on in the Settings dialog, which you can access in the menu at the right edge of the menu bar. Here's a screen shot. Now when you expand one of your friends to see what's new, you'll see something like this.
It's important to be aware that there's a limit to the amount of memory you can use to store this outline. But the limit is 5 megabytes, which actually is a lot of space for outline text. But someday you will hit that limit if you don't delete some tweets.