how long should you be a broad member?
There is no “one size fits all” answer to this question. Guidelines have probably been established in the by-laws of the church so you check them. Each church should be set up according to government regulations.
However, much depends on the size of the congregation, the job requirements, and the needs of the pastor and church. There should be no expectation from a board member to serve longer than that which is have been predetermined.
Most churches have a rotating board with members rotating off every so many years. This allows new blood and also offers a way, in time, to remove a troublesome board member. In some cases, a man who serves on the board too long can have a control, ownership mentality which can harm the overall effectiveness of the board. However, if a pastor does not have enough qualified men to choose from, this arrangement may not be possible.