There's definitely something to be said for changing things too often. If you bring a new person into a group, you're going to affect the efficiency of the whole group. To be an effective member of the group and to actually gain a positive effect from the change will take time. If I recall correctly, it takes a minimum of two years to achieve maximum efficiency after a change(don't quote me on that, it's been a while.)
So let's say you change every six years, instead of eight. You're going to end up having a third more efficiency loss over the long run. In years, that would be eight years versus six over a twenty-four year period. During this time, the group will work of course, but there will be less results. So you really want to avoid upsetting the group too often.
This just from a managerial point of view. There's a lot more to be said about the political side but that's such a rotten apple I don't really want to get into it properly but a few points:
1. Somebody put them there in the first place.
2. Somebody put them back there.
3. You really don't want to have people with contradicting goals alternating too often or nothing will ever get done.
4. Usually a bad decision is better than no decision at all.