I have been toning recently but have found myself throwing the solution away soon after putting 6 or 7 prints through it in one dark room session (I tone outside the dark room). Does diluted toner have a specific Tray life? Since the volume I am using is set by the print size, it sometimes seems a waste when I have not made full use of the solution and throw it out. How long would it keep and what storage conditions are best? All advice appreciated!