The hunting grounds length when you cut off tendrils, invade with pirates or do something with Vodiany lasts 1 turn for every building and pop that's in the system but it's the same for all game speeds. It seems rather silly to have 66 turn long hunting grounds on fast when you can easily win in less than 150 turns. Maybe multipliers of 0,25x; 0,5x; 1x and 2x respectively for fast, normal, slow, endless. 1 turn per pop/building seems like a long time for normal too as you can just wait out the war and then colonize and rebuild the system in a few turns.