SLHFF Hummingbird Feeder Fresh Nectar Defender (2 pk)

Has anyone had problems with hummbirds not like the preservative?

Does the bottle show an expiration date? If I don't use it up this year, will it still be good next year?

Should the hummingbird nectar preservative be refrigerated?

Anyone know the milligram per liter concentration of copper sulfate in this stuff?