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#430
The answer to your question is 30 days. However as noted elsewhere you can manually delete it before then if you need space or know for sure you won't be going back to your previous install before then. Here how to manually delete it - Delete Windows.old Folder in Windows 10 Performance Maintenance Tutorials
My needs are different from yours. I cannot afford to have problems with an untested system. I cannot tolerate the kinds of problems that were rampant in the first CU, nor those that are now appearing with the second.
Anyway ... your point is pointless, isn't it, given that corporate environments don't get automatic updates. They're strictly scheduled by the IT support teams, only after the update has been tested successfully and been through change management approvals. They won't tolerate the force feeding that I'll have to endure if I don't find a fix.
My attitude mirrors that of the corporate environment. I'll take the updates later. I'm not in a hurry. And I don't want the updates pushed onto me. So I need a way to gain control, that's all.
If you restrict the size or available free space of the VHD( you could have a custom pagefile larger than necessary, for instance), update will repeatedly fail, and you can hide unwanted updates using Wushowhide.