I have stock fog lights and have had to replace the bulbs a crapload of times. F'N' pain in the ass. I got rid of one foglight (more direct air to CAI) and the bulb went out in the other. Time to lose to other fog light and save myself the hassle.
As for them going out... maybe it's from a sportier suspension (for our car). :shrug:
Fog lights are only meant for other people to see you when it's foggy. Other than that they are worthless, unless you want to see what you just ran over.