The label suggests to only make up the amount that you are needing to use.  On a side note, I will say that one time I didn’t have time to finish spraying the house, so I put the container of mixed product into a dark closet until the next day, shook the sprayer to mix up the product again and sprayed the rest of the house with no sign that it didn’t work.  The reason I mention a dark closet is that the UV light from the sun is what breaks down the chemicals effectiveness.