Mustard does eventually go bad but as long as the mustard remains sealed the mustard can last around 3 to 5 years.
Once you open the mustard it can start to go bad sooner and it's best to use mustard within 3 to 6 months of opening it.
As mustard gets older and you've opened the mustard it can start to turn bad and spoil and become hard inside the bottle.
To keep opened bottles of mustard from going bad too quickly make sure you place the opened bottle of mustard in the refrigerator when you're done using it.
But for mustard that has never been opened the mustard can usually last in your pantry for 5 years and sometimes a bit longer.
But once opened the mustard should be used up within 6 months.