Over the last five years, I've seen articles in papers such as NY Times or LA Times which chronicled the trend toward having two dishwashers. Often the second machine is located in a pantry area and is used for entertaining. Previously, the two dishwasher kitchen was mainly the province of Jews who observe the Kosher dietary laws, which forbid the mixing of utensils used for dairy products and for meat (oversimplification). Such kitchen layouts place both machines in the kitchen, since the primary motive is to wash dairy and meat utensils and plates separately, rather than to provide a spare machine for large scale entertaining.
While two machines may seem like a big extravagance, the articles pointed out that the cost of high grade cabinets is so high that replacing a 24" base cabinet with a dishwasher will mostly offset the cost of the dishwasher.
Other advantages of having two dishwashers include no need for special circuitry that the commercial Miele requires, and the possibility of washing two loads at once, or staggered loads. In homes with larger kitchens, where the kitchen was remodelled or designed de novo, and where losing 24" of base cabinet storage space is feasible, it isn't difficult to allow for an extra machine, and it costs about the same as a base cabinet.
One of the articles I read said that some buyers would buy a high end Bosch or Miele for the kitchen, and use an entry model for the pantry, since that machine would not be expected to be a daily driver. The article showed the comparative costs of a basic Bosch vs. the cost of a 24" base cabinet and concluded that it was close to a wash...as long as the kitchen was built with provisions for a drain, water supply, and 110V outlet at the site of the second dishwasher....but if one is remodelling or building de novo, it's not a costly option if done in advance.
I have relatives in the Bay Area who used to host a family Thanksgiving for 50-60 relatives and strays. They had a fairly large custom kitchen in their new home, they used the formal dining room to set up the buffet, and we ate at tables scattered through their family room and breakfast area. Somehow, we all fit. They would fix the turkey and everyone else (the guests) would bring the side dishes and desserts.
Everyone pitched in to clean up afterward, but the rate limiting step was their sole dishwasher. Dishes were rinsed and stacked on the counters, ready to go into the machine, which of course could not keep up with the demand. A second dishwasher would have been very handy. However, they rarely entertained other than at Thanksgiving, so they probably saw no need for a second machine.
I have a basic Bosch Integra from 2001. Its Quick Wash cycle can finish a load in 30 minutes, though I wouldn't recommend it for heavily soiled dishes. Glasses, coffee cups, perhaps dessert plates can be thoroughly cleaned on this cycle. If this were a second machine, used in a pantry for entertaining
The final rinse is only about 105 F, however, so the condensation off the glasses on to the steel sides of the tub is not so pronounced, as a result dishes and glasses are not bone dry at the end of the cycle.
