Windows 10

[Nadirah]

Life of the device is from the manufacturer's perspective, not yours. If your PC broke, and you fixed it, clearly you could use the original license you had. If you had to buy a new PC, you'd probably get Windows 10 preloaded and the license fee would be included in the cost. This is more like iOS and iPhone versions. Since iOS8 only works on the 4S and higher, anything 4 and below is end of life.

Or you build a new machine and reuse the existing license.