It is important the clay is stored air-tight. After unpacking, repack the unused clay in cling-foil and store in an air-tight box. This prevents the clay from drying.
DaisyClay dries fast when exposed to air. When working with DaisyClay only take the amount of clay you need and store the rest in your air-tight box.
Although DaisyClay mixed with Water Colour can be kept for a long time, it is best you do not make more coloured clay than needed for your project.