None what so ever PAS.
As long as you remember to set it back to your cooking temp.
Daveomak posted to a member about sterilizing her smoker after use. I picked up on that like hound to a scent.
So, even though I live in a fairly dry climate, I do a 275° run before I do any smoking, and before I put my smoker to bed under it's cover.
I usually do 2 hours on either end. Use your own judgement.
Pre-heating, just like the house oven, gets the smoker oven warmed and ready for action. Less erratic behavior afterwards. Eliminates cold spots, if you will.
Post-heating dries your smoker out, burns off any mold causing spores, and is just good practice for a healthy happy smoker.
I usually wash my racks and mats, then put them back in and fire that muther up. Let it dry out the parts.
OH, and during the Pre-Heat, if you use an
AMNPS, fill it with pellets or dust, and roast it in your smoker. Dry fuel never fails to work good. So you get a twofer, happy Pre-heater smoker, and dry fuel for the main event.
Win-Win!