This blog articulates well the idea of mission as central to small group and church sustainability. I consistently wrestle with the concept of assimilation into mission rather than ministry, and the most effective means to accomplish this end.
I’m not sure I’m ready to abandon wholesale assimilation to ministry as a pathway to mission as Hirsch suggests (this is the route that I took, as well as many missional practitioners that I know), but the principle is important to understand.
Sustainability in community is driven by the size of the mission and vision. Groups that are internally focused tend to turn on themselves, and ultimately die. This creates an approximately 2 year life cycle of small groups, which is pretty standard lifetime for assimilation based churches. Once your means of attraction becomes outdated or fails to adapt, thus drying up your source of new individuals, your church is essentially doomed to die.
Only when small groups catch an initial vision to be externally focused will they endure beyond this life cycle, in my opinion.
Read all of Hirsch’s thoughts here: