Faster Flex Compilation with Flash Builder 4.5

The Flex 4.5 SDK compiler is slightly faster and more conservative about memory compared to its previous version. There are a couple of small changes that a developer can make to speed up compilation. One of them involves a new compiler option and others are related to organizing code in your project and can be leveraged by customers on the 4.0 SDK as well.

http://anirudhs.chaosnet.org/blog/2011.06.02.html