Lisa ~
It is best to drink it within the same day. There have been several times that I mixed a shake and left it in the refer over night - it was finer-roo.
I often mix my oatmeal and Homestyle Chili the night before and tuck them into the refer just before I dive under the sheets. The refer looks like it belongs to a mad scientist with the little jars in there.
When I pop up the next morning, the little berries in my French Vanilla Berry Oatmeal are plump and tasty. The Homestyle Chili when allowed to reconstitue is awesome.