Fog Lamps constantly requiring replacement

On my mother's 2000 Intrigue with 48K miles, I have had to replace the fog lamps every 12 months or even sooner. The car is only driven about 5K miles yearly and mostly during the daytime. The car was purchased with about 27K miles on it. I have used both Sylvania regular and Silver Star with the same results.

Is the problem likely due to the design allowing too much heat building up around the bulb and thus shortening the life of the filament and/or poor filament materials being used by Sylvania? I don't think it's due to the low bumper occasionally strking the ground, though I couldn't rule it out since my mother frequently drives the car alone. Thanks.

my left one kept going bad, finally i noticed water inside the housing. i had to replace the housing to stop the problem - it had a crack on top. make sure you use the proper wattage when replacing them. i think someone installed the wrong one that was too hot for the housing, and the plastic was a little distorted in the area where it was cracked. the housing was expensive $123 each side - i got one for cost plus 10%, still about $85