So you have a schedule trigger that is set to run every night at 1:00 AM or something like that, right?
You can set it up to only run if there are changes to the repositories it uses, or any subset of them. You can even make it only run if there are changes to certain files or folders in a repository.
Look in the settings for your schedule trigger. If you set it up this way, it won't even trigger if there are no changes.