The ATM itself would have nothing to do with an expiry date, nor would the QR code I would not think.
It's all about the bitcoin (wallet) address that the QR code includes.
The address can be seen in digit form at the website too. You could in fact copy that address and then once at the ATM, enter that address. It would be same thing as using the QR code except you'd be manually entering the address.
That address leads to a Wallet.
I guess there could be an expiry date embedded in the address, but I have not seen any indication of one (so far)
Who ever owns that wallet gets the amount when ever the payee sends it thru the ATM or thru an online Exchange service. So the ATM knows nothing about the transaction till the first time you enter that QR code at the ATM. It could be a year from now as far as that ATM is concerned it would not matter.
The only way it would mater is if the owner of the Wallet (Rocket) cancels that wallet for some reason and that would not happen.They may cancel or change Exchange services but they will always have that same Wallet, or multiple wallets.
What the Wallet does when it is asked to create an address is to always create a new address every time that would lead to the Wallet. That way there are no traces that a certain address receives certain payments due to multiple deposits thru that same address, Anyone can see these address' but that is as far as that goes until they get clues like what I just explained. With a new address generated every time a request is made, then there are no issues with a chit load of payments going to one wallet address.
In the 'old days' the ownerof the wallet would have to manually generate a new address every time someone needs to send him/her currency, but that has changed and the wallet does it automatically.
So if you understand all that (I know I can be confusing) but if you follow all that then you'd see that as long as that Wallet exists then the QR code (address) should always be valid.
-Cryptocurrency ATM is a Kiosik .. where Kiosik is a general term for a machine like that.
-Barcode is the QR code. This holds the wallet's address and maybe other things but I do not know what they'd be.
-Bitcoin address is the Cryptocurrency ID Address, which is the address to the Wallet (bitcoin is just one currency of many).