My wife is fussing at me because I've been wearing the same pair of 2 week contacts for probably 4 months now. My experience thus far is to only replace if they either tear or develop irritation. The eye doctor I got my prescription from said it can cause a rash on the underside of the lids. Then there's sites like [this](http://answers.yahoo.com/question/index?qid=20100625164344AAhvoEW). I obviously don't have a rash problem. What's the truth about these?