The longest cycle I can coax out of my Neptune 7500 is about 110 minutes, which works out to 1:40. I use that for whites, and because it incorporates the "stain cycle" it has the added bonus of using hot water (unboosted) for the first rinse. It gets the whites very clean indeed.
There's a limit to how much juice you can coax out of a 15 amp wall socket before the breaker blows. Remember, the electronics and motor use some of the allowable 15 amps, so 1500 watts is pushing it (although plenty of 110 volt space heaters are rated at 1500 watts). At 120 nominal volts, 1500 watts works out to 12.5 amps, which is under the limit, but doesn't leave much room for the motor and the fact that many laundry rooms don't have dedicated circuits just for the washer (the dryer may share the same outlet). Also a 20 amp appliance should require a special plug and outlet - with one of the prongs perpendicular to the other. They are available at home centers but most homes don't have those, either.
A 1300 watt heater will use 10.8 amps, which leaves more room for other loads.