I find dying butterflies depressing. It's pretty much the only thing in the game I find a bummer.
I know singing increases the lifespan of a butterfly a little bit, but not that much.
I can also "animal youth" each one and then feed it back to adulthood...
It would be great though if there was a potion, powder, or something that would give a butterfly (or all butterflies within range) another week or maybe 3 days of life. Then the butterfly lover could just pour that potion every week (or twice a week) and make sure the little winged fiends never expire.