How long after purchase is it advisable to keep processed ketchup and mustard?

Ketchup should be consumed within a year of purchase and mustard within 2 years.
 
An opened jar of ketchup will last 8-12 months if stored in the refrigerator and a month if stored in the pantry. An opened jar of mustard will last 8-12 months, regardless of whether it is stored in the refrigerator or the pantry.
 
Quality may suffer if opened bottles of ketchup and mustard aren't stored in the refrigerator.
 
Mustard will lose its distinctive flavor. The tomatoes in ketchup may begin to ferment and adversely affect flavor.
 
Source(s):
GourmetSleuth.com "Food Storage Guidelines
Ehow.com "How to Determine the Shelf Life of Condiments"