How long does a Vodafone prepaid PAYG sim remain valid if not activated?

I purchased some Vodafone prepaid PAYG SIM cards from Amazon a while ago that came with 7GB data preloaded. Some had £10 credit which you could redeem for a 7GB data bundle and some had no credit but had the 7GB data bundle already applied.

Does anyone know how long they will last before they expire, assuming they haven't been activated yet?

Here's a link to the Amazon listing:

amzn.eu/d/4…FjW