Many professionals who study religion, cults and similar group dynamics, agree that many of the groups that tend to disband or end soon are the ones that predict the ent of the world and the ones who are based on recovery from addictions.
The first one is obvious, as the date where they predict always tend to be in the near future (to appeal to a sense of urgency), and then the date comes and goes and nothing happens. Hence, the group disbands. The WT has been excellent at keeping the date vague and at talking themselves out of a given general date.
The groups based on recovery from drugs die down because a second generation, that is the born-in have never been addicted nor have experienced any of the consequences of addiction. Therefore, they don't see why they should be recovering from something they never experienced.