Can I just stick the cap back in and keep it on the liquor shelf, or should it go in the fridge/a different container? Does it last indefinitely?
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Kevin Zraly says two weeks for sherry and just days for a fino. Keep refrigerated. I keep it much longer but only use for cooking, not sipping.
I agree with latoscana. If you're actually drinking it, treat it nicely, but for cooking, there does seem to be enough alcohol to stay fine for a long time on the shelf.