It depends on the size of the glue joint and the size of the parts attached. Tiny part and small amount of cement used, at least a few hours.
Large surface area and big parts, (wings to fuselage, or additional plastic strips for increased joint strength,) minimum of overnight. A little poke with a hobby knife tip will tell how hard the cement joint is, if it's still a bit soft, then waiting until a full cure has been reached is needed for the best results.