I need to vent a little bit.
I've had to throw three followers off of my twitter feed in the last week for excessive promo tweets.
The thing is, these people weren't tweeting their own books. They were retweeting other people's - in batches which in one case reached 100 in about 5 minutes, spamming my feed out completely.
There's a common wisdom that retweeting other people's promo links is a polite thing to do. But if you really have to - spread them out. You're not benefitting anyone if people unfollow you for spamming.
Spread them out. Use scheduling software correctly. (The people I had to unfollow were probably using it incorrectly...nobody can type that fast).
Oh, and as a reminder. Never send unsolicited Buy My Book messages to people directly on any social media. That's another thing that will get you unfollowed pretty quickly. And possibly blocked.