Water heaters cycle but you could be causing it to have to cycle more often than it was designed to. They have thermal protection switches and pressure/temperature popoff valves. If the pressure popoff valve fails to function; they blow up. Furnaces are designed to cycle and to heat open spaces safely.
On thing you might try is most campers use mechanical thermostats for the furnace/air conditioner. The DW always fussed about the heater running too long and getting too hot in the camper then getting too cold before it came back on with the old mechanical thermostat. Mechanical thermostats take a wider variance in temperature to turn off and on. Replacing it with a digital type will maintain the temp in the camper more accurately. Now the camper stays within several degrees of the setting with the digital.
