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I am sorry to hear about your loss and this situation. Executors of a probate action in Mississippi have a duty to act timely, but no "window" is given (since each matter is on a case by case basis). As such, someone in your situation can file pleading with the court to ask the Court to order him to hurry up, but then it would be up to the Court to decide how much time to give him and whether or not to set a deadline at all. The Court may also, on its own motion or on that of an interested third party, have the Executor dismissed if the Executor proves unwilling or unable to timely probate the matter or meet certain deadlines.
However, one's relief rests with the Court. Perhaps a letter threatening this may spur him to action without needing to actually file anything, but it depends on him.
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