Digital storytelling tools can produce projects with a long life, but it is important to consider both the format for viewing/experiencing the narrative and the format for editing the narrative. It is quite possible that you could end up with a project that can be shown for many years, but that can’t be changed in any way. Make sure you consider both sets of needs -- viewing and editing -- as you develop your project.
In addition to helping you keep your materials for long-term archival preservation and make edits, keep in mind that this process helps you recover if a certain file type or service stops working. If browsers stop displaying your file type or new tools become common for showing certain media, you want to make sure you can transfer your project to something that will work with as little extra effort as possible. Think how frequently this has happened even in the past decade or so: the disappearance of Flash, the shift from physical to streaming media, and so on.
The Library of Congress has published preferred file formats for long-term preservation. Even if you use a different format for certain purposes -- say, to make it load faster in a web page or to make it easier to use in presentations at conferences -- you will want to make a version in an approved format for archival purposes. This ensures that the story you tell, with your full explanation of your content, is saved. Your goal is a format that is lossless, contains connected metadata, and is readable on multiple platforms/devices.
The exact file format you should use depends on the kind of work you are archiving. Some common types that come up for narrative projects include IMF (Interoperable Master Format) for film/video content, WAVE files for audio, and TIFFs or GeoTIFFs for images and maps.
Some types of narrative projects are especially difficult to format in a way that aids long-term preservation. Video games and software have this problem, as do projects made in some proprietary systems (like many tools used to create story maps). In these cases, you may need to be more creative.
Saving your project in multiple formats, on multiple types of physical and digital media (like a DVD, flash drive, and cloud folder).
Finding a way to document aspects of your project in other formats, like recording a playback or walkthrough with narration or saving screenshots.
Keeping a version without digital rights management.
Saving individual parts of your project separately in more reliable formats: for example, source images, script or text content, base maps, or archival footage can all be kept in separate files with additional text descriptions about how you combined them. You may be keeping many of your elements this way anyway in order to make edits or updates.
You also want to save the content and the individual pieces you use to make your story in a way that makes it easy for you to edit or update your project.
In some cases, these formats will be the same as your archival/preservation versions, but in many cases they will be different. If you are using proprietary tools, you will want to keep versions of all your files in the tools’ preferred formats so that you keep things like editing history, styles, or templates in place. It is common to run across this in programs like Photoshop, AutoCAD, Maya, and other design or modeling programs.
In many cases, you will end up with multiple versions of the same file: one for editing, one for long-term preservation, and one for use in your edited project that may be smaller or in a more accessible format. This is okay, and usually a good idea! Just try to use the same file name so that it’s clear how the files connect to each other, and consider keeping a text file that describes what each file is for as part of your documentation.