To my knowledge, Square runs off the more-generic no expiration policy that many other states have, so the system does not automatically disable cards after a set amount of time. 

In theory, you could clear the balances of those cards yourself, one by one, by going to Gift Cards from the pull down menu, selecting the card in question, scrolling to the bottom of the activity, and selecting Clear Balance. 

But unless your cards specifically have the expiration date written on them, I think it would be a bad customer service practice to do that, and also might not be legal if the wording isn’t there — again, double check the law. Where I am, the funds never expire by state law, so I have cards languishing in the system for years. I have the funds from those in a savings account, earning interest, forgotten but useful.