This chapter comes from the book Continuous Integration: Improving Software Quality and Reducing Risk by Paul Duvall, Steve Matyas and Andrew Glover. The authors aim to help teams make this important practice a "non event" - something that happens unobtrusively and as a matter of course, as opposed to the painfully long build times some teams experience. Long builds and inadequate test suites tend to lead to developer shortcuts and frequent "red" (broken) builds, at which point it's impossible to judge code quality based on CI results. The final result of this scenario tends to be quality-related delays to deployment.
To improve CI build times and test suite maintainability, read the InfoQ exclusive excerpt: Chapter 6: Continuous Testing from the book Continuous Integration: Improving Software Quality and Reducing Risk.