LPT: Laser printer tells you it's out of ink? Put in a new toner, print a page, put old toner back in, print 500 more pages

This is for laser printers that won't let you print because they're supposedly out of ink. My Brother printer tells me this and pages are still coming out perfect quality. If you put in a new toner, print a page, and then put the old toner back in it thinks it has a new toner and lets you print all you want. You can easily squeeze out an extra 500 pages or so.