If I buy a legitimate copy of Windows 7, can I be sure Microsoft will acknowledge its product key?

Sep 9, 2018
I want to buy a real, legal, unused box copy of windows 7. I know they are expensive, but piracy is unsafe and limits how much troubleshooting you can do. I'm not asking for instructions on how to pirate windows 7 safely. What I want to know is, if I buy a legitimate box of windows 7, can I be secure in the knowledge that the included product key will not have been blocked or otherwise discontinued by Microsoft?

I'm not asking how to know if a box is real or not, I'm fully aware that there are risks involved with buying these boxes. I want to know, if the copy I have IS real and unused, can I be assured that Microsoft will accept its product code and allow its activation when I set it up? My worry is that Microsoft will just start invalidating unused Windows 7 product codes to keep people from installing it.
I have heard no indications of MS rescinding keys sold legally and in compliance with their ToCs.

However, some time after support ends, you can expect the activation servers to be shut down. This has not happened yet for XP, but presumably will eventually. 7 would presumably be some years later.

It's possible that they will follow Adobe and release a version with all the activation stuff removed, essentially a pre-pirated version: https://forums.adobe.com/thread/1195856