Just some observations as they applied to my '80 152.
- My landing light is on from takeoff to after landing. On average, each lasts about 40 Hobbs hrs. One burned out after 13 hrs, one lasted 62 hrs.
- My single landing light is mounted in the cowl. The back of the light bulb has a square "bump" that fits into the holder. The holder has three mounting holes drilled at 60 degrees apart. As such, the bulb can be installed with the filament in the horizontal position, or 60 degrees from horizontal, but not exactly vertical.