It seems like you vacillate between 10 and 20 members at any given time.
Van der Sloot appears to vacillate between apologetic and aloof in his response, captured on hidden camera.
I kind of self-edit that out of the history, but they did vacillate for quite a while.
1590s, "to sway unsteadily," from Latin vacillatum, from vacillare (see vacillation). Meaning "to waver between two opinions or courses" is recorded from 1620s. Related: Vacillated; vacillates; vacillating.