|BEST PRACTICE: Don't change the .MM Script!|
It is a good idea to design your script if at all possible so that from release to release you don't need to update your script. If you don't change your script you can be pretty sure that extensive testing of the generated MSI will not be required (as "it worked last time"). This is one of the reasons why information which is likely to change has (at least by default) been split into a separate version file.
For example your script can handle more or less files by using wildcards and the "Files" command rather than listing each file individually. Of course this raises the risk that you may miss a real problem where a file is missing, at the end of the day you will need some testing. In general I think misisng files issues are manageable and will not occur often if you are careful. The risk of a "one line coding change" is as you probably know generally much higher!