Sketching every day is a good habit to get into. Sketching 3 or 4 pages in my sketchbook is a daily thing for me. I recently joined a group on facebook started by one of my professors. They give an assignment and you doodle and post a 5-10 minute drawing. Because I have been going on sketch adventures and working on other things, I've ended up behind in the daily sketch assignments. This is just me playing catch up and getting some digital pencil mileage in.
3-5 minutes or so. Drawn digitally in Sketchbook Pro.