Are you pressed for time? Nutes are kept in separate bottles such as grow part a part b and bloom part a part b because they would cause a reaction if in the same bottle. I have no definitive idea what would happen if mixed 24 hours before but I'd play it safe and mix nutrients as needed. Now some people make organic brews and let them sit overnight but I believe you're referring to bottled nutes not organic.
I have two fifty gallon reservoirs ... I mix three part nutes in one. Leave plain water in the other. I use about 1/3 of that res ever time I water, and I water about once every other day. So ... one lasts for about a week. But, I have to say that I have a small (aquarium) air pump bubbling in both.
Been doing it that away for decades ... no problems.