First, make sure you have the full access and information of the accounts so you don't get locked out of them. Seems to happen quite a lot lately.
As many have pointed out, you'll want premium anti-detect browsers, quality residential proxies or mobile proxies, and make sure each profile is totally isolated. The less accounts per one proxy instance, the better I suppose but it'll mostly come down to how well each profile is isolated and your access habits. That'll minimise the chances of losing an account to detections.