Is it possible to delete staves mid-song?

In my choral arrangement, the first quarter of the song has 3 voices/instruments, so I need 3 staves. But the last 3/4 of the song is only one voice, so the other 2 staves are empty.

I know it's possible to make the other 2 invisible, but unless I'm doing it wrong that doesn't help with the spacing - I'd like to delete the other 2 after they exit so it's just 1 stave, which would use much less space.