All competitive advantages have:1. a limited life. 2. unrestricted sustainability. 3. protections against imitability. 4. the ability to earn above-average returns indefinitely.

The answer is the ability to earn above average returns indefinitely

Explanation:

To earn above the average returns are form of returns in excess of what an investor expects to earn from other investments with similar amount of risk. This gives an ability to manufactures to produce at the lowest cost, which is an advantage to organizations.

1) a limited life.

Explanation:

Competitive advantages create core competencies, but as time passes, what was one your competitive advantage and your core competency can turn into a core rigidity and make your whole business go down. Consumers demand more and more nowadays, and what is considered a good service today might be considered a poor service tomorrow.

E.g. Kodak had the competitive advantage in the production of photographic film, but as digital cameras became popular (and then cell phone cameras), Kodak didn't adjust its business strategy in time and went broke.

i would say their habit of breaking down.