So there had to be a reason that they could not survive indefinitely outside.

For many reasons, scientists believe that life on Earth cannot survive indefinitely.

There isn't any crisis: the system looks good for 40 years, and with a bit of extra resources can survive indefinitely.

Additionally, he could no longer survive in space indefinitely without an air supply.

With water and our kits we should be able to survive indefinitely.

As such, she has the ability to breathe and survive indefinitely in either air or water.

You've pretty well convinced me we could not survive here indefinitely.

For another, he could survive indefinitely without food or air.

"There are many organisms that could survive here indefinitely without our assistance."

No matter that these systems are often too expensive to survive indefinitely in their present form.