My BX is rated at (If I remember) to run at appx 3,300 rpm. If I am going to 'work it', I run just below, perhaps 3,100 rpm. If I am just moving the tractor from point A to point B on flat ground, I might drop it to 2,500 just to quiet the racket.
I come from a racing background and 10,000 rpm was just the beginning of the power band where a rough idle was 3,000 rpm, screaming was over 16,000. Lugging hurts my ears. Those poor pistons slapping around as it struggles, those rods being over stressed.