How long after purchase will store-bought hummus remain good to eat?

It depends. Assuming they are unopened, some pasteurized hummus brands will keep up to 18 months  after purchase. Other pasteurized brands will keep up to 90 days. The differences in shelf life are the  result of varying pasteurization methods, as well as varying uses of natural or artificial preservatives. (Citric acid and sea salt are examples of natural preservatives. Sodium benzoate and potassium sorbate are examples of artificial preservatives.)
 
A growing number of pasteurized hummus brands are shelf stable and do not require refrigeration.
 
The shelf life of unpasteurized hummus also varies. Brands that contain preservatives may keep for up to 60 days. Those that don't will keep for only a matter of days. Brands containing no artificial or natural preservatives are often marketed as natural or organic, assuming the brands conform to the additional guidelines or standards  required to qualify for these designations.  Preservative-free hummus brands typically require refrigeration.
 
Some processors of unpasteurized foods contend that pasteurization destroys nutrients and is simply used to extend shelf life. Processors that don't include artificial preservatives contend that the preservatives can adversely affect human health. Because hummus is marketed as a healthful snack (and, indeed, it is), it isn't surprising to see brands that are free of artificial preservatives. 
 
Source(s):
Entrepreneur "Chemical Preservatives Extend the Shelf Life of Hummus"
Wild Garden "What is Shelf Stable?"
Mediterranean Delights "The Pasteurization of Hummus! Because Not All Hummus Is Created Equal"