I've worked all my life in the engine industry, design and development, and I also habitually run my engines at higher speeds every now and then.
The most common mechanical issues with engines are to do with regular slow/cold running, start/stop and 2miles to the shops once a week etc. Something run on the motorway all day will suffer far fewer issues generally speaking.
Piston ring and valve sealing benefit from being run at reasonably high speeds every now and then. Do it once the engine is fully warm and it'll cause absolutely no harm at all, don't worry, modern engines will run all day at max power if you really want to.
A typical engine durability test will be 500hrs cycling between max torque, max power and max speed. They'll do it happily and be in perfectly good condition at the end.
Valves usually start to rotate at around 3000rpm typically (varies engine to engine, but that's typical). It helps enormously to maintain effective sealing if the valves rotate to even out the seating and remove any deposits. Similarly using higher speeds helps keep piston ring grooves clean and the rings free to seal properly.
In my Mk.3 CVT Jazz I select S and use the paddles to choose a lower ratio, 4th say, and hold it at 4000rpm for a couple of minutes while on the motorway.