1. A controlling method for an image forming apparatus which includes an image bearing member on which a latent image is formed, and a developing unit that is capable of being spaced apart from and brought into contact with the image bearing member and that develops the latent image formed on the image bearing member in a state where the developing unit is brought into contact with the image bearing member, and the method, which includes executing a plurality of post-processing operations after completion of a first image forming operation, comprising: a step of starting a return process for executing a second image forming operation, when receiving an instruction to start the second image forming operation in a period of time from starting a first post-processing operation of the plurality of post-processing operations, which includes an operation where the developing unit is spaced apart from the image bearing member, to starting a second post-processing operation of the plurality of post-processing operations which is a subsequent post-processing operation of the first post-processing operation, without starting the second post-processing operation; and a step of starting the second post-processing operation when not receiving the instruction to start the second image forming operation in the period of time from the starting of the first post-processing operation to the starting of the second post-processing operation.