I always tested bulbs for 100 hours in the shop before using them. It's really frustrating to have to climb again when a bulb has infant mortality.Ah yes, those bayonet base incandescent tower beacon bulbs. One in the top half of the beacon, and one lower. One has to climb above the beacon, loosen that giant wingnut, swing the top half of the beacon over carefully, so you don't break the lens. Then, with nothing to hold onto, lean down over the edge of the beacon housing twisting the bad bulb out of the socket. Eight out of ten times the glass envelope breaks off, leaving the stuck bayonet base in the socket. Following that moment of dissapointment, you get to spend the next fifteen to thirty minutes trying to deform/twist the bulb base out of the socket with a pair of needle nose pliers and penetrating oil. The wind is usually blowing hard, and sideways snow is always a bonus. Generally I'd replace both bulbs at the same time, even if one was blown out. When you own your stations, you do what it takes to save a few hundred dollars.
I built my own beacons with help from a shop that normally maintained refrigeration and ventilation equipment for stores and warehouses. Two bulbs on a bar, with a circuit that never totally turned either one off, but alternated between them. It met the local aviation authority requirements, and I got over 5 years of bulb life off of them.
Always double check the tool belt before climbing, too. Nothing like going up a few hundred feet and finding that the screwdriver or wrench that opens the lens is missing.