To me, tipping is a very, very personal matter ... so you do whatever feels right. However, be aware that if you stop the auto-tip, anything you hand over to the service staff ... your cabin steward, waiters, etc. cannot be kept by them. They have to turn it into the tip pool. Also, from what I understand ... and of course, this is just conjecture ... the service staff gets "hassled" by management if someone stops the auto-tip. Management assumes they didn't do their job properly.
What I would do if it were me is just leave the auto-tip in place (assuming, of course, you are satisfied with the service provided to you onboard), and then if someone went waaaaayyyy above and beyond to provide you with a great cruise, slip them some greenbacks before you get off the ship.
That's what I do.
Blue skies ...