A good ensemble can give an excellent performance – within narrow parameters.
The right space. The right amount of warmup. The right standing arrangement. The right specific cues. The right time of day.
A great ensemble can give an excellent performance – regardless of parameters.
No matter the space, amount of warmup, standing arrangement, cues, or time of day.
Of course those things still matter; but a great ensemble makes them matter less.
The goal, then, is to widen acceptable parameters for performance. One of the methods is time – repeated performances can make many parameters moot. But more important are practiced consistency and the intentional disruption of familiar parameters.
If you only practice in the evening, book a morning performance! If you always stand in sections, surprise your ensemble with a mixed arrangement. If they become reliant on your cues, stop conducting or let someone else conduct. Sing in all kinds of spaces, as often as possible.
Ensembles acquire many routines that are not obvious – it the conductor’s job to recognize them, and intentionally disrupt them, in order to help them move from good ensemble to great.