What size bulb are you using and is there a lot of moisture in the fridge?

We are using a standard appliance bulb. We have not noticed any more moisture than normal.

The other thing you can check but it has to be unplugged when you do it. And that is check the socket on fridge. If the base (small tab at bottom) isn't touching good enough or there is corrosion it can caus bulbs to burn out early.