It will keep getting thicker and more sour as it gets older because of more and more probiotic activity. If there is no mold on it, I will use very sour yogurt to make Kadhi - a chickpea flour and yogurt dish.

I do not add fried dumpling in the dish. Instead I add spinach and winter melon and cook it. It really tastes very good.

https://www.vegrecipesofindia.com/punjabi-kadhi-recipe-punjabi-kadhi-pakora/

At least a week-10 days for plain yogurt. It may have lasted longer but we always finish it before then.

A friend made and dropped off homemade yogurt. I've eaten it for a few days now with no issues. But how long would it last before it goes bad?