There is no expiration date for cashier's checks. If a cashier's check isn't cashed in a timely manner, considered six months by most banks, it can be considered void or invalid.
Some banks print "void after" dates; however, funds can be reissued by the original purchaser in the form of cash or a cashier's check.
Banks are required to report to the state when funds or property have been abandoned, typically after five years. This is known as the escheatment process. The state then becomes the owner of the account, funds or property, treating any proceeds as state funds. Valid claimants can make a request to reclaim unclaimed property, at which point they are refunded the value at the time of escheatment.