when i was looking at celicas before i bought mine, the dealer said that because the headlights are angled in a long slope, it causes condensation more frequesntly than in a standard headlight. so, the reason it's so common is because it has to do with the shape of the headlight...given, it doesnt happen to everybody, but everybody is at risk. you can take it off and re-seal it as many times as you want, but it could still happen.
Condensation comes from moisture inside. The shape has nothing to do with how moisture got into the headlight unit. If it was the shape of the headlight, then BOTH headlights would have condensation in it. Tell your dealership to go to school and pay attention next time. Fu*kin moron.
Sorry, stupid people make me really mad (the dealer in this case, not you cwsample).