I think it depends on what you put in them. Obviously can't make a frozen smoothie the night before. If you use blueberries it can make the smoothie coagulate, and if you use soymilk the acid in the fruit can cause it to separate.
^ yup. And if you put bananas in it they'll get gross too. You could try just doing a berry smoothie. It might be runny even if you keep it in the fridge and it would freeze solid in the freezer. Good question though. I've been eating smoothies in the morning lately too and it is loud and time consuming. Not what I want to do at 6am but like you, I' haven't tried making them the night before. I'll try it once this week and see what happens.
You could try assembling the ingredients the night before. I've done that. Just measure out the berries, cut up the banana, and cover it in the fridge of freezer for the night. In the morning you just have to dump everything and some soy milk in the blender. Saves some time and the smoothie is still fresh.