I agree, too much posting is dominating the feed. I too stop following those that post too often.
You also have to consider the purpose of the twitter account. Some are marketers, some are 'bots', some are chatty, some are just news feeds.
Some automated posts are from RSS feeds, so as the feed updates, the tweet is sent. With these, you have to decide if the feed is providing you with value.
Automating the feed for a global global audience awake at different times is good practice.