After 17 minutes of continuous non-stop water flowing & heating the L5 will cut out. If you stop & start the water flow as you work you won't have a problem as the heater resets every time the water stops flowing.
Once the heater cuts out after 17 minutes, all you need do is stop the flow and re-start it to get the heater running again,.. so its not a big deal, just a minor annoyance.
I'm finding I'm stopping the flow less and less, especially on commercial work & it does get on my nerves occasionally.