LIfe of protein/fruit in a smoothie?

I have heard three days in the fridge.  Never let mine sit for more than that.  Could be wrong, but thats what I go with.  BTW, mine are fruit, coconut water, lots of greens (kale, spinach, collard, chard) and vanilla protein powder.  Some recipes use yogurt, and I dont know how that impacts shelf life.

The combination might last longer if you keep the fruit and protein seperate until you're ready to drink.  You could still do most of the prep work beforehand and just toss the powder in the fruit mix when you're ready to go.

Alternately you can just buy something premade like Naked Juice and mix in as mush protein powder as you feel like you need.

The mixture will separate a bit after a few hours or overnite in fridge.  Think how Italian dressing or other oil/vinegar dressing might look when you take it out of fridge.  And the apparent volume will drop because the air will excape out of the frothiness made by your blender or ice will melt.  So, just like the Italian dressing, shake well before you drink it, that will homogenize the mixture.  Also, adding scoop of protein right before you drink it can be good idea too.  

I usually make my smoothies 4 servings at a time (one big blender pitcher) and store in Mason jars.  The wide mouth Mason jar makes easy to pour in protein powder and the top is secure for shaking the mix.  Having the juice covered in fridge is good too, I think.  Plus, everything is washable/reusable.  I have found, though, that adding the protein powder at the time of blending it all works better, because it minimizes some "clumping" of the powder.

Still, I think 3 days tops is shelf life.