A problem in the deliverance ministry is, people ARE seeking instant change while refusing to clean up and walk rightly before God.  These people become very bad problems.  They try to sit on the fence and will use a deliverance ministry to minister to cast devils out with no intention of giving up certain pet sins.   If a person is not willing to walk the walk of faith and holiness before Jesus, don’t waste their time nor yours.
Pray for them and ask God’s mercy.  Don’t let them tie you up casting spirits out that they have no intentions of keeping out.  If God’s not working with them, don’t you either.
Another problem is, many will slip across town to a deliverance minister because they fall into sin and don’t want their pastor to know.  This can be an abuse of the deliverance minister because after deliverance, a person must be taught how to stay free. After the deliverance minister spends hours with such a person, many times, they never see that person again. Unfortunately for that person, sometimes they fall away because they do not take the time to learn how to walk after deliverance. Sometimes, deliverance is instant but the knowledge of keeping it, comes through teaching and learning defense when these spirits try to return, ( Matt. 12:43:45).