It is definitely wrong to belong to a church and worship in another one. This church 'hopping' is not spiritually beneficial.

To convince someone not to go to other churches you need to know their reasons for doing so and reply to every excuse they make. Some would say because our liturgy is too long! St. Paul taught us to "pray without ceasing" (1 Th 5:17).

To dedicate few hours every week to attend the liturgy and pray with others is not too much. I am sure every excuse they give could be easily refuted. One need to have the feeling of belonging to his own church, to feel it is his home. If we are close to our own church and understand its sacraments, its prayers, its hymns and most of all, its liturgy we will never feel we want to know any other church.