I read somewhere on here that the proteins started to turn after something like 10-12 hours, could have been a forum post, so possibly, in fact probably BS.
I think the OP was talking about mixing up a whole lot, the picture I got was a massive punchbowl of protein(Now there's a thought....), that one could dip into throughout the week.
I agree that a whey+milk shake would do fine left to its own devices for a few hours in a gym bag/locker, hell even in a hot car it'd be fine for 2-3 hours, palateablity is another issue. I'm not sure the same shake would last 5 days in the fridge, which is how I read the OP.
I guess I just dont see the problem with water/pint carton of milk added to a shaker/flask and shaken/stirred PWO. BCAA's can be purchased in powder form, as can most other PWO additions people make. These are going to disolve almost instantly in a water/milk mix for the sake of 30s shaking. I dont understand why you would want to blend specifically a PWO shake days before you need it.
I mean, if you wanted to blend a 'breakfast' shake the night before, with oats, fruit, etc etc if you had an early start and a blender would be disruptive, then sure I can see that and I reckon it'd do fine, but who needs a shake blended 4-5 days in advance?!