In my description of my external smoking box:
Mailbox (Popcorn) Mod (with a small twist)
I also described how I clean it after each smoke, using my ultrasonic cleaner. I also clean the "smoke scrubber" which is a metal mesh that traps additional creosote, beyond what condenses on the metal surface.
I also posted about my experience with how creosote build up can (and does) affect the taste of your food:
Cleanliness Is Next To Godliness ... But Does It Taste Good?
So, from my own experience, it is really important to remove creosote build up, if you have that problem. I suspect that those who use more traditional smokers, like offsets, don't have to worry about "gunk" buildup, because it is probably tasty stuff. However, shiny black creosote imparts a numbing, bitter taste to food, and you don't want any of that. Unfortunately, the really, really slow air exchange in electrics, and the nature of how smoke is produced (especially with the factory chip "burner" inside the smoker) means that they produce far more creosote.
So while my "clean after each use" is probably overkill (although my ultrasonic cleaner makes it trivial to do), my food sure tastes better now.
I also periodically clean the smoker itself which, despite using the external smoker ("mailbox mod") still gets a buildup and, when I pre-heat the smoker to 275 before each smoke, I see lots of smoke coming out of the vent, all of it from the stuff (mostly creosote) that is on the walls. That will obviously mix in with my new smoke, once I start cooking, and degrade the taste of my meal.
You can find out more about the significant limitations of using electric smokers at this excellent "science" site:
Summary of electricity as a barbecue fuel:
