If you took the battery out and gave it a bit of a shake the little hydrometer might unstick to let the green ball float up.
But it might not - just means that at least one of the 6 cells is not that healthy, but battery still measures at least 12.6V at the posts.
Starting may not be a problem, but losing charge when left for a few days might mean more chance of strange electronic things happening with sensors and warning lights.
If it doesn't show green after a good highway drive and bumping around potholes I'd replace it - 8 years isn't bad for an O.E. battery.