How long does the Chemotherapy process usually last?

There are a number of factors. The type of cancer, the stage it was in when diagnosed, the chemo agents to be used, and the protocol chosen for the chemo all play a part in determining the length of treatment. In some cases, such as stage II colon cancer in which a single tumor is removed and there's no other evidence of cancer anywhere else, there's no need for chemotherapy at all. (The advantages are insignificant.)