The conversion deadline was today 3-15-18 but according to my broker they can trade indefinitely until all of the shares are to be liquidated in the coming months.
You have figured out my strategy. I have a buy order on the Athens market for tonight. Its low, but if it is slammed down I hope to catch it. Since my sell, NBGGY is down almost 20%. Ill be buying just about the same amount of shares and banking the difference. I didn't see this dip coming.