As a rule of thumb, that's mostly true. It's also true that older LCD panels are more prone to Image Retention (IR) than newer, both because they are older (have more hours of usage--liquid crystals can eventually "wear out" [though it might take many years of continual usage]) and use liquid crystals less-resistant to IR. Also, as a rule, IR is almost always temporary; burn-in (such as with CRTs) is almost always permanent. Of course, the manufacturers of displays simply provide the verbiage of "Don't do this!!!" as CYA ("Don't sue us!!!") for the worst case scenarios. As long as one isn't doing something obviously ill-advised (such as displaying static image/text continuously--such as a grid display), there won't be a problem with IR. However, even if a problem does develop, it can typically be remedied by simply turning the display off for an extended period of time (24 hours, for example). Beyond that there are also utilities and processes which can fix things like IR and "stuck" pixels (even if it's simply displaying a bright, white image for a few hours). The point, though, is that IR is not a problem with non-defective LCD panels given normal usage.