Very appropriate question;
As for me, i didn't need much time either to crush it for the first, second, third...etc time, in less than 1 day of usage, certainly Windows 10 is so buggy especially the Windows Explorer Application, i guess Microsoft noticed that that's why they added the "restart" button to the Windows Explorer Process in tasks manager (it's really bad that Microsoft knows something is buggy and not working but yet they decide to release it -but no wonder it's free upgrade -).
Generally, Windows looks like it uses WPF or WinRT Applications for almost everything, including the Windows Explorer itself, thus making it so Fat and Slow. they have added some nice effects to the apps (such as animations and unnecessary shadows), but unfortunately due to the bad performance of the apps you don't get the chance to enjoy the effects, Apps are barely moving.
As for Updates and Windows Defender, are probably worst decision made by Microsoft as in Windows 10, Even Google Chrome that can be considered one of the best Web browsers is impacted by the annoying compulsory background updates it does, and i can't imagine why Microsoft would want such bad feature on its software especially that Windows Systems are by default buggy and slow without updates.
Whenever my PC gets slow and freezes i know it's Windows Defender or Cortana doing something at background so i go to the Tasks manager and turn them off, unfortunately in Windows after turning Security (Windows Defender) for a while Windows automatically restores it running again.
I noticed a weird thing happening most of the time, when i take a look at the Tasks manager i see the "Windows Reporting Process" running and sending data to Microsoft, i feel annoyed to know what it's sending and why as i didn't approve it to send anything in the first place.
i don't feel safe with Windows 10 at all, i had to use windows recovery twice in less than 4 days, because of their bad updates crushed my PC and made it un-bootable (thankfully i know F10).
At every Windows 10 Run i have to use tasks manager to terminate some background process and speed it up a bit, but i don't use Ctrl+Alt+Delete, As you said :
"Ctrl+Alt+Delete needs it's own Ctrl+Alt+Delete".
After all, i guess due to the new pricing set by Microsoft which most of the time cross the 1200$ barrier, i am highly considering moving to Linux or even Mac which is even cheaper now than that. I told that to a Microsoft support Agent and all he responded was
"Windows is more functional than Mac" but he added that he personally doesn't use Windows 10.
So it's obvious.