DPS tools updated frequently

"Digital Publishing Suite tools are updated frequently."

This understatement about updates starts several of the Adobe DPS online reference pages. The Adobe Digital Publishing Suite tools are being updated approximately every 6 weeks or so, currently at Release v22.
There is a lot of documentation available about the many changes in DPS. You can find out What's new in this release with a list of current version new features to stay on top of the latest developments, view the History of new feature release notes to track the improvements that have been incorporated into previous versions, or see the DPS Bug Fix Release Notes to see the problems that have been fixed in each version going back to v18.

The What's New section of Digital Publishing Suite Help includes links to the Current Release new features, History of new features from previous releases, and Bug Fix release notes including past and planned problem fixes.

DPS updates are a moving target, and that's good! 

DPS Bug Fixes are included in each version release, 

some Mid-Release Hot Fixes are rolled out as soon as available, 

and a few Known Issues are scheduled for a future Fix.

These tools are evolving quickly because they are part of a larger digital ecosystem, and must constantly be changing to keep up with the related technologies. Updates are not just about adding new features and capabilities. Reasons for such frequent updates include targeting new devices (such as new versions of Apple, Android, and Amazon readers), incorporating new technologies (like HTML5), engaging with different platforms (including Facebook and others), as well as interacting with updated Newsstand and Marketplace environments. Improvements in navigation and enhanced performance are always welcome, and bug fixes ensure stability as the software develops.

The DPS bug fixes are even more aggressive in their rollout timing, as an ongoing process of repairing and resolving problems. DPS v20 had two Mid-Release Bug Fixes, and one was less than a week after the initial release date. DPS v22 had a Mid-Release Hot Fix a mere 20 days after it was initially available. There are several Current Known Issues Scheduled for Hot Fix, so another update can happen at any time. Better to fix a problem as soon as possible than wait for the next release to provide the solution!

DPS updates are a moving target, and that's a problem! 

If your DPS tools are not updated across the board, conflicts are likely. You may be prompted to download an update, you may get error messages indicating a problem, or you may crash with no warning. InDesign might lock up, refuse to open or save files, freeze while rendering a preview, stall while uploading to Folio Producer, or simply shut down. Even opening the Folio Builder panel can cause a snag if there are unresolved DPS conflicts, so one troubleshooting suggestion is to use a Workspace without any DPS panels displayed while you're trying to diagnose if that's the problem, just keep you running in InDesign while you check for updates. When investigating a DPS issue, the first recommendation is to be sure that all components are current. 

The most direct way to update DPS tools is directly from within InDesign. Choose Help > Updates to trigger the Adobe Application Manager and begin the download process for any software updates. There are many components involved with DPS, each having their own release cycles. The DPS Dashboard lists available updates by InDesign version (CS6, CS5, CS5.5) and offers download links for the DPS Desktop tools, the Viewer Builder, Folio Builder Panel and Folio Producer Tools. You may also need to update Adobe Air to run the latest Desktop Viewer, and each viewing/testing device will require its own specific updates.

Keeping current is critical

Each DPS version release is an opportunity for improvement. The increasing frequency and necessity of these updates should make this process a reflex to check every time you launch the DPS tools in InDesign. Being sure to have the most current versions installed is critical to keep functioning in the ever-evolving DPS landscape.