Once when my teenaged daughter was doing the dishes, she forgot to add soap to the dishwasher. When the dishes were done, they were clean but did not smell fresh. Ever since then I only add one tablespoon or so to the soap dispenser. It took us over a year to use a 7 pound tub we bought at the warehouse store. - Submitted by Jill
Note: this tip might not work well if you have hard water; you might try gradually decreasing the amount of soap you use.