After 17,000 miles, I've seen 6 bars once--after taking the car to the dealer after the check engine light came on (they "reset the computer" after finding no cause for the light).
The tech said the batt charge was "low" (it had been at 3 bars) and that he'd charged it; only time I've seen 6 bars. I asked the tech if he used a charger; he said no, that he'd just revved the engine.... I now ask service to DO NOTHING to adjust batt charge level unless they find a specific problem and then to ask me first. The tech, btw, did not know how many "bars" there were on the indicator. In his defense, this is a small dealership and the first HAH he'd serviced.

As others have noted, IMA was very active at a 6-bar charge, so active that in very moderate city driving the charge level was back to 4-bars within two miles, suggesting to me that the HAH computer does not see 6 bars as a "normal" level, more an "excess" that needs to be used ASAP. It stays at 3-4 bars 90% of the time; 2 sometimes, and 5 less frequently; I've never seen 1 or 6 from any of my driving conditions in 17k miles. From all that I've read here, this range is more typical than not.
Lewis