Recently, I was wonder if there is a way to increase the lifespan of high pressure sodium bulbs. Is this possible in anyway? If so, would using, for example, a 310W HPS bulb on a 250W HPS ballast increase lifespan of the bulb when run dusk to dawn?

Usually, you can prolong the life of a HID lamp by reducing the power to about 2/3 of nominal. But in the most cases, until you run some special type of lamp like tin type or unsaturated metal halide for example, you quickly end up with a bad color. In the case of HPS lamps, CRI drops considerably already over nominal line voltage variations!