For me I use 2 accounts per IP(sometimes 3) and for my larger accounts I stick with one account for one IP. I used to have 4 or 5 accounts per IP in the past, but nowadays it seems when one of them gets flag for suspicious activities then eventually the rest of the accounts on that same IP will also be flagged in the next following days, it wasn't a big deal but password reset(along with connecting a phone# to each account) were getting annoying especially the twitter clamp down this year.
Again I know some people who have 5 accounts per ip with no issues. It all comes down to how aggressive you are following/unfollowing/liking/retweeting, if it is a young account and the more accounts you have per ip, then the more Risk you are taking. You have to look at what your goal and if is it for the long term or short term.