How long could I stay on the ISS?

Scenario: Aliens hover around the Earth and shoot any craft that leave it. The ISS remains up there with all current members on board. How long would they be able to stay up there like they do everyday without making any adjustments to their meal plans, activities, etc…?

I don’t know the answer to that, but they do have a Soyez (sp?) capsule there at all times so they can escape in an emergency. So in the event that it isn’t possible to launch a ship to take them home from the Earth, or if they need to get out faster than we could send up a rocket, they can still return. I don’t know how the aliens would view an attempt to escape, though.

They have about 5 months worth of supplies. Surely they could stretch that out to 7-8 months.