We make a habit of checking our bill every few days.  It is a lot easier to fix a mistake right away than wait until the last night and have to stand on a long line.  We have caught several errors over the years.  Once we were charged for someone else's laundry.  Another time, the price of a drink was incorrect.  Still another time we were charged a cover charge for a specialty restaurant when we had handed in a voucher for the waiver of the fee.  The last mistake took several days to correct.  I appreciate it when guests can check their bill on your stateroom TV.  We could not do that on the ms Amsterdam so we had to keep getting printouts regularly.  It was a very long cruise.