I have a fair bit of condensation in the drivers side fog light, which was new thirteen months ago. Now the bulb is out. Any tricks to keep the water out, like teflon plumbers tape on the seals? Let me know so I can catch it early!

If yout lens is glass or plastic; check carefully for a possible "stone chip" hole or crack.

The fog light lenses are glass on my 97 so I assume they are the same on earlier years. I've only replaced both sides of the car since my wife had a habit of running the front up on parking light dividers. You can remove the whole assembly with about two screws and give it a good look-see. If the lens is cracked, probably not much you can do to save it. Some silicone might seal it up for a while. The lamps cost about a hundred at a discount new.
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97 S90 with 188K miles still going strong

Greetings:
Although you could have some leakage around the edge of lens or at rear I would suggest looking quite carefully at the lens surface itself. Sometimes a very hard to detect pinhole crack occurs. There are kits to fix these in plastic lenses. Wonder what several coats of Rain-X clear wax would do on the front? A cheap and quick solution, it might just seal around edge or any invisible pinhole. If you run a bulb with water in lens/reflector assembly the water will splash and break a hot bulb.