Not saying to spray soap or anything in the smoker, just remove the grates. Clean and spray or wipe then season.
I dunno, myself I clean the smoker after each use, or if I got lazy from eating all the good food I just clean it early the day I am getting ready for my next smoke.
Task #56, clean as you go (it was a dumb restaurant rule)
But that's just me.
One time I cleaned my grates but not the sides of the smoker, smoked some things and it was good, but just had a bit of a strange flavor. Although that was the very first time I had used apple wood. Usually I use hickory but that time I mixed apple with it. Not saying that the apple was the strange taste so I figured maybe the stale build up of smoke on the sides of the smoker.
You have to figure the build up inside goes bad, sour, bitter, stale, something. When you fire it back up again the heat and smoke would naturally pick up any residual flavors leftover.