Your follower got disturbed? How many times you retweet for one day?
If you retweet just once for 1 day, i think your follower not be disturbed. I've experienced before it, but some of my follower interesting about that. Its about what time you make a post on your twitter.
I suggest to retweet your campaign just once a day. Better time is sleeping time to retweet something like ICO.

Just 1 tweet per ICO and I have joined about 10-20 ICO

so totally I have to tweet/retweet 10-20 ICO per day.
Thank you for your responses guys, but I mean there are many people who do not know what the heck its cryptocurrency. Before we offer about ICO, I think we should tell them first about what the heck its blockchain technology, cryptocurrency, bitcoin, ethereum, erc20, how it will work and give us a profit or help our financial to gain wealth, and so on.