the best thing you can do for your monitor is to turn it off at the end of your normal usage patterns. if that is not an option then having the monitor screen go black upon power save is the next best thing. a good time limit is 10-15 minutes of inactivity unless you use it for movies in which case 30-60 minutes.
the only lcd monitors which i believe were easily succeptible to burn in were the very first ones. also note that crt screens of the same era were also succeptible to burn in.
i agree that you shouldnt have any burn in issues unless the screen is on a static image constantly. even when using a pc monitor for 9 hours a day there shouldnt be burn in.
before i started using a television as a screen i used an ips monitor. whenever i get up for a long period of time (30 minutes or more) i shut down my whole system, monitor included. if you are away then there really is no use wasting power. consider that your pc can be drawing 330w+ just sitting there doing nothing isnt it worthwhile to rethink the "always on pc" ?