If I buy a Windows 10 product key and receive it on email, is there a time limit for me to use it within?

[jamspls]

I'm ordering all my parts to build a PC now, but I don't want to order the Windows 10 key too early - if that's even a thing, because I'm worried it will 'expire'.

Does this happen?

 

[CountMike]

I'm not aware of any expiry limits if it's legit Retail key. If it's some shady OEM key, someone may use it before you do.

 

[Shaun o]

One you have bought a windows licence key as long as you don`t loose it.
You can activate the windows 10 version of the os 32bit or 64 bit from the home edition to the pro edition.
And use it for a life time if you wish to activate windows 10.

It does not expire as long as it is a valid licence key for the Os.
And you can install or wipe the working os to install a fresh setup if you ever change or upgrade the parts of your pc system such as buying a new motherboard and a cpu at a later date Jamspls.