Drawing from life is really key to become better drawers,illustrators and painters. To me it’s a basic fundamental that often gets over looked by many painters. Its like not knowing the words of a song before you sing. When life drawing I prefer starting with 2 and 5 min poses to warm up and then working up to 10,15,20 and 30 min poses. If I am painting however its nice to have half the day to push the paint around.