Don't believe anyone that tells you 'This is the limit' -- twitter doesn't have a # limit, it has an algorithm based on account age, activity, number of followers, historical behavior, and specific unfollow / follow behavior (you can unfollow slightly more people if you're unfollowing people who DO follow you and not just the ones who do not follow you back). This will always be trial and error (I have a batch of 10 accounts that I use very aggressively to find out what the limits are like, then I use the hard lessons I learn with those accounts on the other accounts that I own) but if an account is important to you, GO SLOWLY and be prepared to get suspended, then appeal the suspension and you will likely be fine.