I make them the night before all the time!
I just recommend eating it within 48 hours OR freezing the leftovers in ice cube trays to easily blend back up fresh in the future.
To paraphrase Michael Greger from nutritionfacts.org on this issue, you need to prepare your food in such a way that you will eat it to get the most nutritional value.
Perhaps a SMALL amount of nutrition is lost when making them in advance, but 100% is lost if we don't eat the good food at all because either we didn't like the way it was prepared or didn't have time etc.
So please prepare your smoothies and other food in advance and do not worry about the negligible loss of nutrition.