Paetec PI space?

Hi, We have a customer who was assigned some PI IPv4 space by Paetec back in mid-90's and who has continued to announce the blocks, even though their relationship with Paetec ended a long time ago. Is this a common situation? Does the customer risk having that space reclaimed by Paetec at some point, or is it safe to assume they will continue to be able to route trouble-free for years to come? Thanks, Adam