I assume thats an expected life duration or a value given so that most will last longer. Such things usually follow a normal distribution but much more data is needed to do any calculations andthe ones required will vary depending on whether you give us sample data or population data (mean and standard deviation).

Your question would still be impossible to work out as it is a random process. For weeks you would expect no failures then nearer to 9000 hours you would expect much more. So what time period are you talking about?