To extend the run time, get larger extra capacity batteries. Going more than two batteries is recommended. Also, figure out how many pounds you will be carrying and get a large boat, but a small boat will ensure more runtime improvement. Taking a moderate load and not going at top speed will help the battery to last. Also, keep in mind that these aren't car batteries, so oil the motor often. Something like distillate marine diesel will be the best fuel option if you want to keep a powerful trolling motor at your disposal. Adding a trickle charger will also help a deep cycle battery to last longer when it is close to depletion. Weather conditions like hot weather or significant cold can also affect the runtime positively or negatively. Batteries that utilize solar panels can also increase the runtime.