You should be able to keep it a week or so, but after that, I'd think the flavour would start to deteriorate, even if it hasn't spoiled. Spoilage will really depend on how careful you are with keeping it uncontaminated. For example, once you've put some out for people to eat, don't return the leftovers to the main container. Use a clean utensil to spoon some out of the container. And, as someone here once memorably said, "keep your grubby fingers out of it!"

I have made hummus with cider vinegar instead of lemon juice, and it seems to last even longer.

But I should mention, if you have more than will be eaten in a week, you can freeze it.

Two weeks or even three, if it doesn't get eaten up faster. Just don't let people double dip. I'm convinced that's why things go fuzzy--double dipping!

I've been adding roasted jarred peppers from Turkey sometimes when I make hummus, and I don't see any difference in keepability. I feel comfortable in the 1 - 2 week range, in the fridge of course.