"Note: If you have not changed your code or assets since the last debug IPA package was generated, Flash Builder skips the packaging and debugs the application. That is, you can launch the installed application on your device and click Debug to connect to the Flash Builder debugger. This way, you can debug repeatedly without packaging the application every time."
This appears to not be working in Flash Builder 4.7. It always worked fine in 4.6. Basically it packages the application every single time I click Debug, regardless of whether anything was changed.