Allen from my experience they run together through most of October. Though, later in the month the groups tend to be somewhat "loose" in that they stay in the general area together but start to split off by bedding in different areas or feeding seperately. It seems that after they shed their velvet you start to see them gradually change into the looser grouping. I've seen some of the bucks that must be really good buddies stay together until the rut. Just my experience and that's not saying much.
Scott