Until it forms slimy chunks at the bottom of the bottle...then throw it away. But seriously, I read somewhere it only lasts 3 weeks open in the fridge...but I have kept using mine WELL after that time frame.
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3 days.
Tequila can last indefinitely in the freezer without going bad, as long as it is sealed properly.
Indefinately often
7 years
It depends on the ambient temperature.
Blackberries (the fruit) will last about three months.
I don't know, but it'll last for a long time in the freezer.
Butter can last up to 12 months in the freezer. See Related Links.
Lemon juice will take a couple of hours to freeze in a traditional freezer. The exact length of time with depend on the temperature of the freezer.
3 months
about 2 days