I had this desktop custom built about four years ago; it runs Windows 7 Home Premium, and how it differs from every other version of Windows 7, I couldn’t tell you.
I can, however, tell you this: about every fourth Tuesday, Microsoft serves up a plateful of updates and then pesters me until I restart. If I let it do its thing, the “Logging off” screen appears, and the little percentage indicator comes on. It gets to 30, always 30, and then shuts down. One power-up self-test later, you get the cute little Win7 light show, and the numbers start again at, yes, 30. I figure this is purely arbitrary, but I may never know for sure, especially since Microsoft says it will quit supporting Win7 after the first of the year. I have already downloaded a Windows 10 install and paid for a license. (Please don’t ask me which version.)