Guys, I got the reply from Poloniex support. Here we go: "ARDOR will indeed be credited accordingly with the number held on average during all snapshots. As I understand that would not require them to be in your account at all times or on the actual distribution date but I can not confirm that this is 100% the case. I do know balances will be credited and withdrawals of ARDOR will be allowed, but we are unsure of a permanent listing at this time." So basically I would hold my NXT's up to distribution date