It depends which caps you are talking about. There are a set that do not change until 5yrs old.
My boy retained a cap on one side and the adult tooth grew up behind it pushing it out at a funny angle. The vet just gave it a tug when he had Reeco sedated for Xrays and it came away. The Cap on the other side is showing no progress in falling out but the adult tooth hasnt erupted yet so I'm not worried. Vet said if he still has it at 7 or if the adult tooth grows under it then they will tug it then.