How long can you keep sweet pickle brine without cucumbers in it? Or can you even do this? I use sweet pickle brine in many of my recipes.
As the brine is the preserving agent (due to the acidity, even in a sweet pickle), not having the cucumber in the jar will not reduce its shelf life.
The brine should easily last six months (and probably much more) in refrigerator.
I've kept it for months in the fridge (mostly bread & butter, but occassionally from dill pickles or sweet gerkins) ... not sure what the max age is.
I'm guessing the most important thing is to not have contaminated the brine (ie, use clean utensils when extracting pickles, and not to use your hands or anything that's been in your mouth)
And for those wondering ... I use it to add moisture to chicken salad or tuna salad, and for vinagetette when you'd have otherwise added honey or another sweetener. (you'll have to taste & adjust, though).