Yes, one year is the maximum validity period for a payment link. If you wish to modify the link expiry, you can set an expiry date suiting your business use case at the time of link creation. One year from the date of the link creation is also the default link validity set if you do not specify an expiry date.
In case you wish to modify the expiry date post creation, you can choose to update the link with a new expiry date or immediately disable the link using the expire link API.