What to think about when you conduct

Just because.

"There is a limit to the speed at which we can repeatedly shift our attention. The maximum rate at which a conductor can give cues and/or transmit expressive details is an absolute value, independent of the tempo of the music. Experience has shown me that this is approximately one instruction per half-second. At mm. = 120, that amounts to a cue every beat; at mm. = 60, two cues per beat. But this value is an upper limit: It is difficult to sustain for more than a few measures without making yourself dizzy and drowning the ensemble in excess information. A more comfortable rate for both conductor and ensemble is one transmission every one to two seconds—allowing for momentary increases or decreases in the rate when called for by the music's structure." daqui.