Conference day 1: clean shaved faces. Nice open hair. Hugging people you haven't seen for a year. Asking your overseas colleagues how the jetlag is doing. Slowly starting up discussions, with mostly senior folks involved.
Conference day 4: stubble. (Unwashed) Hair in braids. Rings under the eyes. Quietly nodding to each other over the third cup coffee before the start of the first session. Heated but friendly back and forth in every discussion session between everyone.