Me and my wife work different shifts. She works days and i work nights. So basically our LCDTV is on approximately about 12 hours a day. My question is could they withstand this much hours everyday? How long will they last? From what i heard they have life span of 60,000 hours so that's about 15 yrs?I have a Sony 40XBR2. Thanks.

You are correct. The marketed half-life of most lcd, as well as pdp as far as I know, displays is 60k hours. This would be @13.7 years if the set was on 12 hours a day, 365 days a year. Something else could fail before the display or you may just want a newer set earlier than 13 years.