Do you want to put your TypoScript into files (because you'd like to put them into your scm or you want to separate it from the content for easier deployment and development?) AND use the t3editor at the same time? Try my new extension "TypoScript Files" (Extension Key: tsf). Grab the code from the forge svn or from the TER.
The extension hooks into the t3editor and into tstemplate_info and inserts the content of files linked with <INCLUDE_TYPOSCRIPT: ...> while still preservering the information where the content originally comes from. After saving the content will be extracted again and copied into the original files. This allows you to edit your TypoScript files within the t3editor.
Recursive nesting <INCLUDE_TYPOSCRIPT ...>s also works.
Or: Let your TypoScript files be automatically created by simpling wrapping the part that should go into a file with "### <INCLUDE_TYPOSCRIPT ...> BEGIN" and "### <INCLUDE_TYPOSCRIPT ...> END". After saving this goes into the specificied file while the database record will contain only the INCLUDE_TYPOSCRIPT reference to that file.