The question of how long will Windows 10 continue to run as a free upgrade has been unsettled. The obscure wording "we will keep [Windows 10] current for the supported lifetime of the device," has been interpreted to mean that as long as your computer will run it, it will run. That is obviously a meaningless tautology, since MS has it within its power to make a version of Windows that will not run on any extant machine, but given that Windows 2000 will still run on a lot of brand new computers, it did not seem like a big issue. Recent reporting is showing that MS considers the lifetime of a machine to be from 2-4 years, and that following that, it will likely force an upgrade to a new version "Windows" that will be a subscription not a perpetual license/purchase model. Presumably those who have taken advantage of the free upgrade to Win 10 from Win 7 or 8 will have burned their license to those perpetually licensed versions, and now will be forced to pay forever for "Windows." Those who still have a licensed copy of the earlier versions will be forced to go to subscription when end of support life is reached for those, or face using an unpatched and insecure OS.
 
http://www.computerworld.com/article/2945796/microsoft-windows/microsoft-to-provide-free-upgrades-to-windows-10-for-2-to-4-years.html
http://windows.microsoft.com/en-us/windows/lifecycle
 

You have 5 to 10 years (a more recent article here):
http://www.theregister.co.uk/2015/07/20/windows_10_support_lifecycle_announced/
 

Yes, it does look like the end of extended service is 2020/2025 (see link above) -- which used to mean you would get security updates through that time. They have not given up on the strangeness of supported machine lifetime though, it has moved to a footnote. I take this to mean that at some point prior to end of support, your device may no longer be able to get security updates if it somehow becomes obsolete. By packaging security and other updates together the fine distinction presently between end of support and end of extended support is blurred. And how will MS tie your machine to the OEM Manufacturer's support period?
 
** Updates are cumulative, with each update built upon all of the updates that preceded it. A device needs to install the latest update to remain supported. Updates may include new features, fixes (security and/or non-security), or a combination of both. Not all features in an update will work on all devices. A device may not be able to receive updates if the device hardware is incompatible, lacking current drivers, or otherwise outside of the Original Equipment Manufacturer’s (“OEM”) support period. 

I'm not seeing this as a change from earlier versions of windows. Looks like business as usual to me.

I was looking at laptops the other day. My kid is about ready for a new one. I grabbed some CPU numbers from the machines I was interested in and looked them up on the Intel site. All of them were marked as discontinued except for the i5 and i7 models. All the machines I was looking at were new, so I'm thinking that Intel makes a run of chips for a particular company, say ASUS, and then dumps the template.
 
Corporations seem to think we have very deep pockets and an endless taste