I had 3 NB extract kits from 2010 that I forgot about. They were stored in a plastic tote in my basement which stays between 65-68 degrees. Brewed them all and they came out just fine. Maybe not award winning but very drinkable just the same. I made an Alt, an English pale ale, a Lefse Blonde (which looks more red than blonde but I don't mind), and a Belgian dubbel which is in the secondary right now. I'm sure the others are correct that you may want to use the LME sooner than later to avoid off flavors, I guess my (and SWMBO's) tastebuds weren't able to detect any issues so I guess I got lucky.