We have three year Board terms.
Officers and Committee Heads are voted annually, so they could change that often but the goal (hope) is keep them for at least two years.
I am a proponent of longer tenures. Just when you go about learning something, you're off the Board / Committee and some new, well- intentioned guy has to get up to speed.
Those that suffer the most in this cycle is probably not the Members but more likely the staff, who are constantly re- educating Board members and suffering through their "good" and "new" ideas.