It is supposed to be some kind of regular meeting with all discussion about problems that group have or might have when SHTF.
It is impossible to have useful group if you actually do not know how that group act. It is one thing to imagine how people will be and react from your group, but reality is different.

Since you can not know how people react before SHTF, you need to know them as close as you can.
So regular meetings, or even some kind of practicing together (it can be only camping trip or similar) will show you some personality of the people in your group.

I meet folks from my group regularly, every week, I know them very well, I know their weak spots, they know me.
Of course it is easier here, since most of them are veterans from the war, just like me.