Viability and the Small Church

A Church Consultant in the USA has asked me what I think about "viability" in small churches – how do you decide when a church is no longer able to continue?
I try to avoid the term as too often it is associated with finance which assumes a paid person is needed to babysit the small church. That approach is anathema to my thinking. If the congregation believe they have a mission and have the will to give it a go then the wider church should be facilitating them - not asking questions about viability... Theologically, limiting viability to finance doesn't seem to me to be a Gospel approach... I hope someone will do some real work on that some day.
Viability should be tested in terms of the members in the setting - can they do the basics: look after the property, the services, manage the offerings, prepare for communion - I had a specific list once but you could make up your own. Or they could. The problem is not with the congregation if it wishes to continue; the only problem is re-defining "viability" and developing a ministry strategy that works.
Viability might also be related to other members in an adjoining church which might be willing to offer some support. Our Russell congregation continues on a regular base attendance of only four for at least two reasons:

1. It is a seasonal church and for several months of the year there are visitors.
2. Members of our Paihia congregation see Russell as a challenge of mission so the worship leader hardly ever goes over on the ferry alone.

I don't think that sense of being a “mission situation” is a bad thing for an isolated congregation as long as the local people can prepare the church building for worship and Communion and handle their own banking and the other basics. And, I suppose, as long as their generous offerings meet the normal maintenance on their property.
But by most conventional criteria of “viability” I guess Russell doesn't qualify to continue past next Sunday.