flash actionscript: I find that when I make a change to an external as file, the changes don't take
effect in an swf that uses it without republishing the swf. Why is that?
What's the use of as files if I have to republish the swf anyways? (aside from
separated view and model).

Because at compile time all code is compiled in one swf. You don't use external
as files the way you use include files in server side software - for example.
External as files are for instance useful when working in a team so each member
in the team can work on the same project. Another thing is you can use an
editor of your choice. Some like SEPHI, others use Eclipse with a plugin for AS
and there are other editors too.

you don't need to change anything in your swf to have changes take effect.

it does tend to be in the browser, but even if I clear my cache after uploading
to the server it still happens. I can't remember the last time this happened,
though, so maybe I'm just crazy. Either way, thanks for the help.