Contrary to popular belief, dishwashers are designed to be more efficient than hand-washing dishes. On average a person uses four gallons of water every two minutes washing at the sink where dishwashers use less than four gallons per cycle. In the long run a dishwasher could be more beneficial not only to your water bill but the environment. But there remains the question of how frequent a dishwasher should be used.
On average, the number of dishwasher cycles per week in a household is about five. Surpassing this number could increase the need for repairs or a replacement in the long run. A typical dishwasher will last about 10 years. If you can cut down your cycles fewer than five per week your dishwasher could last 12 years or more.
While running a dishwasher everyday of the week may not be best for the longevity of the appliance, it could be more efficient for water use and the environment.
Source: Apartment Therapy