No that's exactly right. I'm specifically referring to your [0] comment. It allows me to spread the compilation over a longer time (days) while being able to use the old things without breakage. Before, I had to recompile everything and things would be unworkable until everything was recompiled. I now have a number of boxes with distcc so compilation times aren't that bad nowadays. But back in 2010 or so, when I just had a shitty gateway laptop, dealing with libpng version bumps was a weekend affair.