While I do not have a MES 40 electric smoker, the same should apply.
Many moons ago when I first started smoking, I asked my local health inspector, this very question. Her response was; as long as you do not leave drip pans, or dirty racks in the smoker and allow mold to grow, no deep cleaning is required. If mold has been allowed to grow in the smoker clean it with a bleach solution of 1 cup bleach to 1 gal of water, and rinse well. If no mold has been allowed to grow Heat the smoker to above 300 and hold for 30 min.
I always heat my smoker to above 300 and hold for at least 30 min, even if I am cold smoking. I have NEVER had any problems, following this advice. The only time my smoker gets a bath is when I start seeing grease build up in the bottom, or it has set for a long period of time, and then it’s off to the car wash for a bath.