[240 2NR]

The gaskets fit between the back of the lights and the body of the car.  It's function is to both secure the lights (as evidenced by how hard it is to remove them) and to keep water out of your trunk.  So the fact that they don't fog up says little about how well it works to not replace the gaskets.  You may want to check beneath your trunk carpeting to make sure you in fact don't have any water penetration.

Also I think it's a bad idea to recomend cutting corners in an install, let someone decide for themself, but don't annouce that leaving out the gaskets will not lead to leaks as gospel.  Personally I see no point in saving $5 and 5 minutes on a $400+ mod  that you have to live with for the rest of the time you own the car.