erio,
It should be dependent upon your driving routes, and on how you drive. I'm surprised to hear that it was often at 8 bars when new. Was this once or twice? If so, it could have just been coincidence. 8 bars doesn't happen to me very often - usually only when I coast down a very long hill, assuming the SOC was already up there around 7 to begin with. Of course, coming down a mountain pass in Tennessee one time I didn't have any trouble getting it to 8 bars, but that's pretty unusual for me...

I wouldn't be concerned at all, unless you see it doing something strange.