This is ok for a single developer or even a small team. Once you get to larger scale development, you usually want to keep code generated artifacts separate for the source code that generated them. Often you never want to check-in generated code. Why? Because then you have two sources of truth: the artifact (WSDL in this case) and the generated code. You don't want to have to keep these things in sync manually, you want your build process to do it. So you don't check in the generated code, and your build system generates it instead.
So ideally the code generation in Flex Builder could be invoked outside of Flex Builder. This may be the case, but so far I have no luck in this. It is certainly not a documented part of the SDK.
I looked for an alternative and found wsdl2as. This looked promising, but did not work out. First, it expects you to send in XML literals when sending SOAP messages. Sure it generates the boilerplate around the core message, but if I wanted to work directly in XML, I would not have bothered with a code generator. It has an option that seems designed to deal with this, but did not. Even worse, it does not handle anything except the simplest WSDLs. The first WSDL I tried with it defined complex types for the input parameter and return type of the web service. This caused wsdl2as to choke, as it expected any type information to be inlined. Sigh.
