What Andrew said. Is there a scriptural basis for "terms" of service for elders/deacons? If not, by what authority does a church limit the service of a man called to be an elder?
As a side note, I find it hard to believe that, even in a congregation of 2000, you have enough qualified men to serve as elders to be able to fill a Session, AND have 25% of the men rotate out every year. I looked at your church's website. Currently, you have 19 men listed as Ruling Elders (
Link). Assuming you plan on keeping the Session the same size if term limits are imposed, that means between 4 and 5 men rotating off the Session every year, and 4 to 5 men coming on to Session every year. You would, at a minimum, need 5 more elders than what you currently have, but I'd be suspicious that it wouldn't always be the same 4 or 5 men coming on/leaving Session, which means you would need new men to fill those empty spots. It sounds like an easy way to force unqualified men into the office of elder simply because you "don't have enough guys".
(In case anyone was wondering about the math, like I was, a congregation of 2000, with 19 ruling elders is a ratio of 1 RE to every 105 congregants. Assuming women and children make up about 75% of that number, that means one man in every 26 men is currently serving as an elder. If you add just 5 more elders, your ratio of elders to men in the congregation changes to 1 elder for every 20 men in the congregation. Now, maybe y'all in Tennessee are blessed with an overabundance of qualified men, but I'd be hard pressed to find 1 man in 20 in California that is qualified and called to serve as an elder.)
One final note: Will the Teaching Elders also be rotating out every 4 years? Why not?