Each 3 weeks, a new build is released for DPS 2015 with new features and bug fixes. When these new builds are released, should we be updating our Signing tool, and any other Adobe provided DPS 2015 asset that we may be using?
No need to update the signing tool, it rarely changes. If/when it does it's typically just to provide better error messages for signing errors we see in the wild, not to change the core underlying signing mechanism.
If an update to the signing tool is required it'd be listed in our release notes.