There are several different ways of receiving deliverance. Some people receive it instantly at one event and everything is cast out. Others go through a long process of deliverance as some people have more intricate demonic issues.
You can liken it to a hospital visit. Someone who has appendicitis goes through a pretty straightforward surgical procedure while someone with a brain tumor would need a more intricate surgery and possibly more surgeries over a period of time to completely remove the cancerous mass. This is because the mass is intertwined with the person’s body. In the same way, demons can also be intertwined with a person’s mind, emotions, physical body, behavior, and attitudes.
Sometimes after the first deliverance session, a person who needs more deliverance may still experience manifestations until the whole process is completely finished. Others who may have had demons attached to them for a long time and have gotten so used to the feeling of the manifestations, that even though after the demons are gone, it’s a comfort issue to willingly fall back into the same dramatic behavior that always happened when prayed for. In such cases, that person needs to be counseled that he is truly free and no longer needs to behave in such ways because it does not glorify Jesus for all that He has done in his life.