Yep, these like to rev, and you can spin it as fast as you want for as long as you like, within reason. They don't have an especially long stroke and the whole valvetrain is set up for use at much higher speeds than our motors will ever see, since it's all the same layout as in a gas Audi or VW that spins to 6.5k or more. In the Volvo, the stock gears are pretty short so cruising at 80+ means the tach reading is up there. As long as the motor is straight and healthy (valve clearances, cooling, etc), it will happily do that for hours without complaint.
