You could probably encode the MP3s with a lower bitrate.
You might as well test if playing from the beginning helps and if removing the fade helps too. I'm not aware of any performance issues with those, but I don't usually do anything like that.
In the case of the fading, you can open your MP3 in an audio editor and add the fade there so that Flash doesn't need to handle it.
I'm assuming that you're not starting from the beginning because the MP3 format often adds a little bit of silence at the beginning of the file. I was able to work around this by making the file a WAV instead. Then, I added the WAV to the library of a Flash Pro document and exported it as a class for ActionScript. I believe Flash Pro ultimately makes an MP3 from it, but it adds some magic sauce to make the MP3 work without extra silence at the beginning. Then, if you're using Flash Builder, you can embed the symbol from the SWF with [Embed] metadata. It's kind of complicated, but it's been working great for me.