Storage time involves the time it takes for harmful bacteria to build up. If there are no harmful bacteria in the hummus it won't go bad. Keep it cold.
Four days seems to be the limit on fresh foods, including hummus. The liquid starts to separate out and the garlic starts to taste funky. You are best to make sure to eat your hummus at it's peak within 2 days.
If you are keeping homemade hummus in the fridge, it should last up to five days. Therefore, it it best to freeze the hummus if you have made a large quantity.