I'm also torn on whether to open certain tins or not. The obvious, I bought them to smoke, but once I smoke them, then they're gone for good. Which makes it hard. I also have a bunch of tobacco's in mason jars to smoke from already, so I don't want to add more mason jars to the tobacco cabinet. Usually, I'll smoke through several jars before I think about opening a new tin. The discontinued blends I do have open I smoke from sparingly (i.e. McClelland - Christmas Cheer), and when I do smoke them I make sure I sit back and enjoy.
When the news broke that the Sutliff and Mac Baren blends would be discontinued, I went through my tobacco cellar to verify what I had on hand, and then I went out and bought a few blends I wanted to have a few more tins of. Just so I could have those blends to enjoy for a little bit longer.