Look if you are coming across an exchange that is asking for KYC only on withdrawal and does not list the same on their terms and conditions then stay away from that exchange. But in general as time progresses we are not able to keep bitcoin or altcoins decentralized to that extent that we expected to keep them. More and more exchanges are popping up with new regulations and they are asking for KYC all of a sudden with freezing of funds on non-compliance. This happened with poloniex some time back and then Shapeshift as well asking for membership and then KYC.

It would be better off for you to do your own research and withdraw stored funds because you never know when you favorite exchange comes up with new rules. At that time you will end up in a soup. If you are unable to do KYC probably in future you wont be able to transact through exchanges anymore.