I have seen "term limits" on Elders in one church, and in another there were no "term limits." There are no term limits prescribed in Scripture, but I think it's good for a congregation to reaffirm it's officers regularly. Even the best elders may stray, get mired up in sin or false teaching, or otherwise disqualify themselves. Re-affirming elders on a regular basis is far better than appointing them for life.

"First among equals" is a phrase often used to justify the unbiblical distinction between "ruling elders" and "teaching elders" in PCA churches, but it is poorly defined and all too obviously misapplied.

In the Reformed Baptist church I'm a member of, the council (of elders) receives recommendations from the congregation, examines the candidates, and trains them for over a year, rather like an apprenticeship. Those who successfully complete the training are then set before the congregation as qualified candidates, and the congregation votes to approve them or not. My church has 5 elders, all equals, all teach and preach and shepherd the congregation. Two are on the payroll as those "who labor in the Word and in doctrine," and it is they who do most bot not all of the public teaching and preaching.