If there's anything an exchange will do with such, that is they'll thank you for being active since you've given them too much from the fees of your trades and whatnot. Never heard nor read about such. Closing or disabling of accounts are often done on accounts that have incorrect/fraud verification and suspicious activities/scams. As long as you're verified with your true identity and complied with the exchange's ToS, your account would be fine (unless it's Bittrex, lol).
Lol, it seems bittrex is becoming the most messed up exchange right now.
I read some news some days back on how they are trying to clamp down on pump and dump groups and they even included it on their TOS. That sucks though, but that is their terms and anyone who does not want that should use another exchange.
However, like you said, there is really no need for anyone to get banned for too much activity as that is how the exchanges are making money anyway with the fees.