Add option to limit undo stack

I often work all the day long with inkscape with large files and the unlimited undo stack makes Inkscape uses as much memory as it can, This way the other applications have no enought memory and Inscape becomes slower and slower while working because of the use of the HDD. Please add the option to roll the undo stack with the past N amount of actions or to a certain amount of memory ( like Gimp does ). Actualy I'm obliged to close the files and reopen them to free sometimes up to 600 Mb.