It amazes me how much good copper pipe my fellow plumbers waste by scrapping it. Basically, a piece of clean copper pipe does not become scrap until it is shorter than a make-up piece for that particular size of pipe.
I drill holes in scrap lumber we find on the jobsite and use it to make a copper nipple tray of sorts. I save hundreds of dollars a year (including the small investment of time) by having short copper pieces organized and available when I need them.