I like the idea of pulling a vacuum.
But what is the cost savings of keeping old brake fluid, waiting for it to be used, vs tossing and buying new, after say 1 year? I mean, is this stuff really that expensive on a per-gallon basis? I know it doesn't magically go bad after a year, but if you datestamp the bottle when opened, and you get out past a year, is it really big money to just toss?
Worst case, once that year rolls around and you didn't have the spate of brake jobs you had planned more, everything gets a brake flush, 'cuz it's free fluid that has to get used up.