All relationships need time together – new or old, personal or professional. Spending time together allows for rebuilding of bonds, creative growth, airing of grievances, and the sharing of viewpoints.
It’s true in romantic relationships, collaborative professional relationships. And in creative relationships – large or small. Choirs need time together.
I think that the reason that school choirs make the best music of the year in April and May is less because of the growth they’ve made during the year (though that’s part of it) and perhaps more because the members have spent sufficient time together to grow a musical relationship that can support their music-making.