While we highly recommend you trim your wick to 1/8″ – 3/16″ (3.mm – 5mm) for safety and for the health of your candle, you don’t have to do anything you don’t want to do.  We do recommend you at least break off the charred pieces of wick once it and the wax have cooled or before you light the candle again.  This is for both safety and for aesthetic. A tall wick means a tall flame, and that is dangerous -- plus the black charred crackle wood (if let to get big enough), could pop and send black ash onto its surroundings.  Additionally, we’re sure you’d rather not have black bits floating around in your pretty wax.