My younger sister refers to this as "Percolation", as do others (http://www.learningassistance.com/2005/june/percolation.html).

Sometimes, I need to sit with an idea for a week or so before taking action, and the product is great, albeit somewhat rushed. This gets me in trouble on occasion, but less often than one might think.

I've found lately that working piece by piece well before deadline gets about the same quality of work done, but I also have bigger projects and more generous deadlines now.