I should let people select play speed, slow, medium, or fast, and split the world into three sets, assigning you to 1, 2 or 3 depnding on the option you select. You could pay to switch worlds. If you go on holiday, you go to slow world.
Production happens twice a day in slow world, 8 times a day in fast world.
I could make people pay to use fast world. This is all for future scaling, of course.