One would still have to stop to pump the water from the aux tender and also refill the displacement lubricator. Miniature live steam is all about the balance of water, fuel and steam oil. Some engines are designed to run out of fuel BEFORE the boiler is empty, so a stop would be necessary for topping up fuel and water plus steam oil. Twenty minutes or so is considered reasonable run time for many gauge one engines. Larger engines have axle pumps for boiler filling from larger capacity tenders and will also have larger capacity lubricators for longer running times.