Cracks running lengthwise aren't usually a problem. If they bug you, you can fill them in with liquid superglue. Visible cracks running across the limb are often just cracks in the old lacquer. You'll need to really check them out closely though, to make sure they're only in the surface finish and not in the fiberglass below. If they're only in the finish, just keep shooting. If they're in the glass, hang the bow up cuz it's telling you it's retired and doesn't want to work any more.