A hook up at my local supp store called me to say that some old jugs of my fav PP (HDT 5plus 1 Whey) were going on sale ($6 for 6 lbs) because they were about to expire in the next few weeks. And I was about to buy them, but thought I should ask what happens after the "sell by" date. Clearly, PP is not like milk and it goes bad, but does it lose the effectiveness? Is it a waste of money? Thoughts please. Have to jump on this today!