Well here is a small example of what I mean:
I did this yesterday morning mainly in one sitting, just playing. Now you may ask yourself what does this have to do with cleaning off your palette, well he was done from paint left over from a couple of days of paint on my palette from another painting that I am working on..........as some of the paint was still viable and wet, I just sketched the face out onto a boar and then started to paint him in with that paint before I scraped down and started back into the other image. A cleansing of the palette as it were, and not wasting of paint.
Could I go back in and tighten things up more and turn it into a "finished piece, sure I can tighten him up, but for me he is finished, served his purpose and was a good exercise, and to be totally honest, I like him as is.
So the next time you have to scrape down, maybe see if you can lay some more paint down and just play a bit..........it is fun, and sometimes you get something out of it as well besides a clean palette.