When you build a large project, it is often important that previously built components that are still up-to-date are not rebuilt. Otherwise, if all targets are built every time, each build will take a long time to complete.
The longer it takes to make a build, the later you get feedback on your changes, the more difficult it is to setup reliable and meaningful Continuous Integration process.
And the faster your builds are, the higher the rate at which your changes are integrated, the less is the feedback time, and the more value you get from your Continuous Integration.
TeamCity 7.0 introduc