According to ComputerWorld, Microsoft has decided that their 30-day rollback period is too long, and so they reduced it to 10 days with version 1607. Honestly, 30 days seemed a bit too long to leave (in my case) 30 GB of crap laying around your main drive, especially considering a new build is dropped to the public once every six to nine months or so. They should have an interface for users to easily delete early, and maybe even a power-user tool to move it to external storage or something.
This should not affect users who upgrade from Windows 7 and 8.x, unless the rules have changed since the November (1511) update. A non-Windows Insider machine will only install a new build of Windows 10 if the previous install was a clean install, or if the rollback period has already timed out. Also, users can still return to Windows 7 or Windows 8.x by performing a clean install with their respective product key, and Microsoft still provides ISOs on their website even if the user lost their install DVD.
That said, Microsoft still should make this much more clear in their interface, though. Looking at the Settings page, above, there doesn't seem to be any indication that my time is running out. Not cool.