Bears live primarily in the forest and they have a remarkable way of adapting to people moving in to their territory. Black bears eat berries, nuts, tubers, roots, honey, worms, buds, leaves, fruit, twigs, grubs, fish, insects, and small mammals. In the spring, black bears even eat the inside layer of young trees. They must eat between 11 and 18 pounds of food each day to stay healthy. Black bears hibernate during the winter months.
Water should be boiled for at least 3 to 5 minutes to sanitize it. Some agencies recommend boiling for 10 minutes just to be safe. If you live at high altitudes, add a minute for every 1000 feet above sea level.
Armed with all of those (probably useless) variables, my anecdotal answer is that it should take around 15 to 20 minutes to bring six quarts of tap water (temperature) water to a full raging boil. I suspect you have a very low end stove and (possibly) stainless steel cookware. 50 to 70 minutes is far too long.