You could sit at 5200rpm for hours going down the motorway, and no harm will come to your engine. The ecu controls the rev limiter, which is there to stop the engine revving to dangerous levels.
Your engine could probably cope with upto 6800rpm for a few hours, but the rev limiter is set below, for a few reasons. The main one being, that the power drops off after 5500rpm, (when you tune your engine, this is why a "chip" will raise the limiter, as the power band will probably raise, my GT limited at 7300rpm!!!), so there is no advantage to rev over that, and keeping the revs lower, will help reduce componant wear. Also, engines are fine revving under load, but they don't like "free" revving as much, though as long as your not one of these numptys that sit in a car park on rev limiter in neautral, I wouldn't worry.
It's not advisable to keep hitting the limiter though, as the engine slows down and speeds up again very quickly, a few times a second, which means more stress on the engine.