What is the biblical basis for lifetime eldership? Some churches who appoint elders do so for a term (3 years is typical from what I have seen). Other churches ordain elders for life. Is there a Biblical basis for ordaining elders for life?

This is a follow on to my question about term eldership.
I would believed that this issues falls under church polity. The conduct of the local body of Christ is not always clear in the Bible. There are no verses, that I know of, that state how long the mandate of an elder most be. Historically, an office was hold as long as you qualify to it. A carpenter would be exercising the same profession all his life. This is why I think the Bible does not tackle the question of a term. 

In today's thinking, we have the idea that power corrupts, and therefore is almost a sin to hold a position of power, and the influence of our political model might be the reason why we are considering this question.

From a Bible perceptive, as long as an elder fulfills the requirements from Titus and Timothy, I do not see a biblical recommendation on the question of time or term. This question presents another aspect of our Christian liberty.

This being said, elders have a huge responsibility. If an elder does not qualify, not merely as a result of a sin, he should give his resignation (not wait the end of the term) to protect the glory of God in the local body. (The idea I have in mind in this case, could be a young father that cannot take an adequate time with is family. A husband that is always out of the home. These are not sin, but that they are unwise may be patent.) 

http://www.9marks.org is a good resource on the question of church polity. I know that I am greatly influenced by them in my thinking on this question.