QR Code consists of 2 types which are:

• Dynamic/One Time Payment/Fixed Amount QR Code = Upon creating QR, you can set the amount on how much your customer should pay. The QR Code can only be paid once afterwards the QR Code will be inactive.
• Static/Multiple Payment/Open Amount QR Code = Upon creating QR, you did not set the amount hence your customer can input the amount themselves on their end. The QR Code can only be paid multiple times with no limit, hence always active.

Hence for Dynamic QR Code does have an expiry time! It will expires within 48 hours if there is no payment coming in by default.

But it can be set via API using parameter "expires_at".

As for Static QR Code does not have expiry time since it can be paid multiple times and always active to receive payments.