6 months??? How big is that tub of protein? The protein I buy usually lasts me a month or less. There's a reason for the "best by" date. Sure the protein will be fine most likely for a few extra months (better to be safe than sorry for the company), but if there is an expiration date, it is probably bound to go bad at some point. That said, like Hort mentioned, protein powder usually does last for a long time, so you might be fine. (And I'm sure you'll be able to tell by the taste if\when it does go bad.