Note that this question
is about suet (unrendered kidney fat from cow), not tallow.
was never answered before on this site; this question specifically does not say anything about unrendered fats.
Therefore please refrain from closing this question as a duplicate of either of those aforementioned questions.
The question really is: how long can raw unrendered beef suet be left in the fridge? Suet when rendered is called tallow and can be left outside for about a year, but what can be said of suet when not rendered and left in the fridge?