This is very pretty. Like Luis said, there is a feeling of baroque, although I also thought it was rather like a hymn. I particularly like the contrasting dynamics in measures 80-85. I'd like to hear this sung by your friend, if you ever get the chance to record her.
I was trying to review some orchestral scores to get an idea of breathing and pauses, and looking at Tchaikovsky's 1812 overture, from the measure 332 (which is like minute 12:25 in the video) the woodwinds have very few pauses, and I actually counted sections of more than a minute without a silence. In some parts they play almost like the strings.
Here is the score if you prefer it:
Perhaps the director or the woodwinds section organise to take turns to play without loosing breath?
I am looking for such a extreme example in brass. I counted up to 20 seconds in the brass section without a silence (perhaps I did not not a longer section?). Suggest me some other composition.
What do you think about this case? Does this demonstrate that woodwinds indeed can play for minutes without a silence?
It's hard for me to say exactly. Any brass instrument will need to breathe more frequently if they are playing in their highest register. This is the best I can give you:
With trumpets, I would say that unless they are playing high in their register breathe shouldn't be a big problem. The instrument is small and cylindrical, so there isn't much resistance. I would say a trumpet could play for about as long on a single breathe as the oboe mentioned by gylfi, maybe a little longer.
French horns and trombones would require about the same amount of breathe, I think. They definitely cannot play for as long as the trumpet on a single breathe. Bass trombones will need more breathe than tenors.
And the tuba takes a ton of breathe to speak, so any tuba part will need pretty frequent breathes.