Now in project,it is not recommended to put your code on the frame of the Sprite/MovieClip expecially not the main timeline. So this topic is quite like a Brainstorming.
For the linkage MovieClips all are not on the Stage,we can not simply Ctrl+F in FlashIDE and replace the target string. Suppose that there are thousands of linkage MovieClips in the Library,have you found any way to solve this problem?
1.Create a new MovieClip instance A on the Stage.
2.Select all of the Symbols in your library(expect the Symbol created in Step 1) and drag them into the MovieClip A.
3.Ctrl+F on the Stage now to find and replace.
4.Delete the symbol A from the library and it has gone with its own instance,with all of the temperary instances generated in Step 2.
Done!Flash needs you be smarter to do it right.