does gulitimne go bad?

Assuming you mean glutamine...i'd pay attention to the sell by date.
Yeah, pay attention to the sell by date. I would still consume it over a year by that date. The stuff doesn't turn to chicken poo on 12/05, and they are very generous with those dates. On 12/05 (hypothetically) 99% of their stock needs to be good. So, a year later maybe 50% has deteriorated to 90% purity. With proteint I wouldn't care much. Vitamins or steroids I'd be a little more weary.
It also depends on what climate you live in. I live in the northeast, and I've had it turn to crap just because of the humidity. Even in a sealed container, it's still going to get some moisture out of the air. I don't know if it really went bad, but it certainly had a hard time mixing with water. I just ended up throwing it out and buying a new container.