Hi, welcome! There's a thread very similar to your question that's only a few spaces down. http://community.basenotes.net/showthread.php?t=207691
Try using the search feature, it works wonders
But to answer your question as long as you keep the EDTs in a cool, dry place out of the sun you can expect it to last more than 4 years. I'm not too sure about the "more natural" colognes though, some turn faster than others.