From what I understand, the issue results from the breakdown of lysine. But I think we're talking over period of several months, especially if it's stored in a hot environment.
Drink up, you'll be fine
You are a smart muthafcker. Just sayin'
I don't recommend doing anything that I do or have done, but here is my experience. I have or had loads of pills and powders that expired as far back as 2002. Like Adipokinetix. For the most part, stuff well past its expiration just seems to be ineffective at worst.
I had used protein powders that were at various points past their expiration and these are a little bit different because they are powders and not sealed in caps. If it is bad, I mean REALLY bad, you will know. It will just taste horrid and you probably won't drink enough to get sick from it. That's if it hasn't gummed up or hardened to a brick already.
It may be less effective, but it won't make you sick to try unless it is really bad.
IME, if I found a tub of protein in a cabinet that was stored in a dry spot and was, I don't know, 12-18 months out of code- I would mix it up and use it. If it was 19+ months....I would be more hesitant.