how long to keep an opened jar of half sour pickles in refrig?

I just opened my partial container of half sour pickles that were purchased from the cold deli case. They are about 3-4 months old, and while they appear to be okay, the skin is clean and clear and not slimy, the pickles leave a sharp tingling on my tongue, which means there is a different fermentation process in play, very similar to apple juice turning to hard cider.Personally I don't like this and will toss the rest.

It is possible it could still be good, it's only been four months. However, keep in mind that you have to use Your judgement, which means you need to feel confident about your decision. All I can do is give general advice.

'Sour pickles' don't always have the same food labeling meaning in different countries, but often it refers to pickles that have been fermented in some way. If yours is fermented it may very well be still good. Fermented foods that have not been pasteurized continue to ferment, albeit slowly, when stored in cool conditions like the fridge. Fermented foods USUALLY last for 3 months to 3 years in the fridge after opening, but will loose quality, taste and texture as time progresses.

Then again, many pickles are pasteurized or heat processed. This kills off the bad and the good bacteria. Killing off the invisible nasties (aka bad bacteria, yeast, &c) that cause spoilage is a great reason to pasteurized, but a lack of good invisible beasties (bacteria, yeast, &c) also means that once the jar is opened, there are no invisible beasties populating the contents, and anything can grow in there. Pasteurized foods keep much longer than unpasteurized, in the container, but once opened, pasteurized foods spoil considerably faster than live cultured foods. So even if your pickles are fermented, if they have been pasteurized I would personally defer to modern scientific food safety wisdom (opposed to my more traditional based approach).

Of course, if it were me, I keep pickles in the fridge for upto a year fermented or not, pasteurized or not. Basically working under the assumption that the acid keeps the nasties at bay and if there's no black mold, and it smells good, then I'll give it a tates. Modern safety experts cringe.