There are many factors that play into maximum safe anesthesia time, including age, cardiac health, vascular disease, or the presence of chronic lung conditions. For most patients who are generally healthy, 5-6 hours of general anesthesia is typically quite safe, as many procedures extend well beyond this timeframe, even in excess of 12 hours, without any significant long-term impact. Without knowing more about your overall health, it is hard to say what is safe for you. Be sure to speak to the anesthesiologist prior to surgery to get more information about the type of anesthesia and airway management being used, as these can have almost as much impact of safety as the duration of the anesthesia. Thanks for your question and best of luck!