Invisible 1,
Getting back to your question, IMHO you should set the AH on the ground, adjust the bar, and leave it alone for the rest of the flight. Any thought of caging/resetting the gyro in flight is fraught with problems: as long as the AH was wings level on the ground, the nose up/down attitude will be reflected accurately throughout flight.
Taken to extremes, a two pilot crew who have set their AH horizons to a different datum could create a potential hazard should there be an unflagged instrument failure, whereas a crosscheck to AH's set to a common datum would be far more easily compared to each other, and the standby horizon.
Some helicopters cruise markedly tail down (A109, for instance), and you soon get used to seeing 4-5 degrees nose up in cruise. Your IF skills, as previously mentioned, will complete a full scan of other inputs to tell you what the machine is actually doing.