The challenge is this: balance on every scale.
Check at the scale of a single rehearsal: are you balancing all of your repertoire that needs work? Are you balancing drills and scrimmages? Are you balancing your various educational and social goals?
Check at the scale of a week: are you balancing intense rehearsal time with the calm social-structural components that are vital to your students growth?
Check at the scale of a month: are you balancing the urgent needs of the next concert with the more distant, large-scale goals for the ensemble?
Check at the scale of a year: are you balancing the repertoire you are programming in terms of genre, period, vocal style? Are you balancing performance opportunities with opportunities to learn and grow in other ways?
Check at the scale of a career: are you balancing familiar repertoire with new to you? Are you maintaining a foot in the strong background you have in this art, while growing into new ideas and strategies?
Balance at every scale.