I run Flex Builder 3 on a mac and as my project grows - the compile time gets longer and longer and longer. I am using some SWC\'s and there is a fair amount of code but it
Go to Project->Properties->Flex Applications. All of the applications listed are compiled each time (even though you have a default set). If you remove everything but the default (don't worry, it won't delete the actual files), it only compiles the default app. This resulted in a significant speed up for me. If you change your default app, it ADDs it to the Flex Applications list - adding to your compile time. You will need to maintain this list to get the quickest compile.