You can also think of a 20% project as being the last item in your work queue. When your "real job" is too busy, gets dropped. When you are ahead of schedule,

You can also think of a 20% project as being the last item in your work queue. When your "real job" is too busy, gets dropped. When you are ahead of schedule, it gets pulled out to keep you from idling. It doesn't have to be literally 20% of your time every day, week or quarter, although some people structure it that way in practice.