I've always wondered why people wouldn't just leave the amount on UNTIL they decided it was too much (or too little).
I suppose if you know you want to tip in cash, then remove the amount, but if not, give them a chance to earn your automatic tip. If they don't, remove it or adjust it at the end of your cruise.
Carnival Elation March 11
Carnival Imagination Sept 07
Carniival Sensation Dec 06
RCI Sovereign of the Seas Sept 06
Carnival Miracle Sept 05
Carnival Glory Sept 04
Carnival Fantasy Jan 04