I have only 2 exchanges, and that is Bittrex and Binance but I usually use Binance since my funds are already there. I'd never had the intent to withdraw once I have profit but just have to keep in there. Maybe I was confident of their security that is why I have no worries even I store my funds for a year but sometimes I also think, What IF...what of the previous hacking scenario will happen again.
There are only two things we need to consider the potentiality of that certain exchanger and that is their security and transaction fees.