Burn ins

Do you mean burnt ends?

If so, one of my favorite pieces of a smoked brisket. Like candied beef!!

Burn in may refer to Seasoning your smoker. Most manufactured smoker have machine oils and/or protective coatings inside the smoker that have to be burned out. A couple of hours at 275°F+ will get this done. Additionally, a smoker will impart a better flavor the more there is a buildup of Smoke Essence in the smoker. Sounds crazy but an old well used smoker makes better tasting Q then a new unit. Adding smoke wood for an hour or two after the initial burn in will get your first smoked meat tasting pretty good.  Smokers made of any type of steel that will rust needs to be seasoned like a Cast Iron Pan. Opinions vary but spraying or painting the interior with any edible oil or animal fat following the 1st burn in, good time to add smoke, will go a long way toward avoiding getting a rusty interior...JJ

"Smoke essence"... Love the term. You should copyright it (if not already taken by the liquid smoke industry).