Just wondering why Travel Buddy dosn't have an insulated door and if fitting one would it have an effect on the life of the ovens electrical components due to heat buid up as some of the heat can escape via the door I may be over thinking it not sure.
To answer your question: cost I guess.
The amount of heat loss through the standard door would be minimal, certainly not an easily measured task in regards to it's energy consumption.
The marine is thermostatically controlled, once it reaches temp, it shuts off. When the temp drops. it fires back up.
Fitting an insulated door will allow the oven to get to temp marginally quicker and hold that temperature marginally longer before it turns back on.
It will have no effect on the lifespan of the element, nor the other electrical components, cause they are insulated from the oven anyway.
Which brings you back to the top of my circular post.