It depends on the material. Also, some lathes top out at 2000 rpm (or less) while others will reach 4000 rpm. So 1/2 power on one may be full power on another.
For most pens and wood, I change speeds usually twice. 2500/3000 speed for rough turning; 1500- 1800 for smooth turning and rough finishing, 800 - 1200 for final sanding, finish and wax/polishing.
. . . at least that is what I am now. []