Microsoft has reduced the I-changed-my-mind period in Windows 10 by two-thirds, cutting it from 30 days to 10, the company confirmed.

Users who upgraded to Windows 10 were able to roll back to the preceding Windows as long as they did so within 30 days. To make that possible, Microsoft stored the older operating system in a special folder on the device's drive, consuming up to 5GB of storage space. After the grace period expired, the folder's contents were deleted.

With last week's Anniversary Update, aka version 1607, the 30 days were reduced to 10. (Microsoft identifies its major upgrades using numerals representing year and month of the release.)

Microsoft said that the behind-the-scenes change had been triggered by data gleaned from the voluminous telemetry it collects from Windows 10 devices. "Based on our user research, we noticed most users who choose to go back to a previous version of Windows do it within the first several days," a spokesman said in an email. "As such, we changed the setting to 10 days to free storage space used by previous copies."

While there was no reason to doubt Microsoft's explanation, the timing of the change was almost certainly driven by the July 29 expiration of the year-long free upgrade offer. With that deal off the table -- and retail prices for an upgrade running between $110 and $200 -- there was less need for a generous trial because fewer customers would be upgrading.

Microsoft itself had linked the roll-back and the upgrade offer, and used the feature as a "get out of jail card" when critics panned the company's aggressive campaigns. Microsoft regularly pointed out that users could restore Windows 7 or Windows 8.1 within the 30-day span if they were dissatisfied, thought they had been pressured into upgrading, or believed they had been duped.

Windows 10's return period -- which lets users roll back to the preceding OS -- has been reduced by two-thirds, to 10 days.

The new 10-day period also applies to reverting to a previous build of Windows 10 for testers participating in the Insider program.