In very very extreme cases an LCD could get uneven wear on those activated pixels. On a consumer level, no, you never have to worry about it. The ONLY exception to this would be a Local dimming LED LCD TVs. These LEDs on the edges would be permanently shut of, thus making the wear on the edge led banks uneven. Edge lit sets, or CCFL are unaffected. Bottom line, your light source will expire before you burn it in.