tankslondon My question is "Can they still activate the sims in a year time? Does the activation code expire one day?"
giffgaff 3in1 sims have never had an expiry date for new account activations, mainly because a mobile number is not allocated to giffgaff sims until the voucher or bankcard payment is processed at registration.
In the unlikely event, the activation code fails, use the serial number on the sim itself, to complete the activation instead. So yes the sims will work for the foreseeable future well beyond a year.
Any change in that policy will be posted in the Announcement thread.