How long would you leave an open jar sitting around and still smoke the tobacco? Despite Forums preference for perfection in moisture content, fairly dry tobacco usually smokes well. Overnight, a few hours, a day, a few days ... usually not a problem, whether it's in an open bowl, in the pipe unsmoked, or in the pipe partially smoked, in my experience. Don't get too cavalier. A blend can dry out and be stale, harsh, burn too fast, or lose it flavor and nuance. Don't abuse the privilege, but generally, for short periods of time, it will be okay, in some cases slightly improved.