No way acerbits. Where do you get your information?
You should turn it off, or better yet, set it up to turn itself off automatically after 15 minutes idle time.
The lifetime of LCDs is dominated by the lifetime of the CCFL backlight, which is dominated by operating hours, not on-off cycles. The less it is on, the longer it will last. CCFLs are rated for 20000 or 30000 hour lifespans - just a few years if you leave them on 24/7.
Plus, turning it off saves energy.
Martin