How long should the bulb last and can I get the bulb # to replace it.

This bulb should last a few years with occasional use. And there is a replacement bulb a lowe's for this.

Did you touch the light bulb with your hands ? This type of bulb cannot be touched by human hands, use paper towels or clean gloves to put the bulbs in. Your hands has oil on it and the oil get on the bulb which causes the bulb to burn and then burn out.