Well, it is supposed to shut off and re-light under thermostat control. Are you saying it happens more frequently than you think it should? That could be a faulty thermostat, or the main thermostat is stuck in the closed position and the ECO (basically a back-up thermostat is controlling the heating. That will result in a continuous cycle of on/off, never staying off for very long. And the water at the faucet is probably unusually hot as well, since the ECO allows a 20 degree higher water temperature.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL