Then there should only be one or two elders on that session -- opps, if only one, that means there are not enough elders in the congregation to have a separately functioning session. So be it; that's better than inventing a "better" system.there may be only one or two elders on a session that remotely remind one of the aforementioned.
While a sabbatical can be quite helpful (our pastor did so a few years ago and we have one elder on sabbatical now) a rotation does not seem to meet the perpetual nature of the office. What's critical here is that God gives the church specific gifts and the men on session, while having the same qualifications, often have different personalities, previous experiences in life, and so forth. Who can predict when the church might need to draw on these resources?