Im able to do 1000 a day on my main account. My accounts i just a couple months old, and haven't ran into a problem with it.
Although i did start a new account a couple weeks ago, and started of slow like doing 200 followers every two days, and unfollowing thos who didn't follow back, and following another 200 or so. Then this last week i jumped to doing 1k every two days (this is how i built my main account witch is still going strong), and i got suspend for aggressive following, a couple hours after i did the a new follow session.
Although i have a feeling i got suspended because i was doing a free promotion of my services that i sell, asked people to mention me on twitter, and they would in return get my services for free. Thinking the people reported my account because, i didnt give them the free service fast enough so they got pissed or maybe it was a competitor that got me banned?
But thanks my experience. Kinda paranoid now tho with my main account, thinking im do about 500 to 800 now instead of doing 1k.