I've noticed that when buying fast food milkshakes the shelf life is highly variable. Some use plastic cups that don't keep it "shake like" as long as the places that use foam cups that seem to keep it "shake like" for oddly long periods of time. Flavor-wise I have some preferences. But for packaging I prefer others. It can take me as much as three hours to finish a shake. I know I'm weird, but some are still mostly frozenish shakes and others are reduced to flavored milk in that amount of time. Thoughts?