I took it out, swished it around and rearranged it every day for the next four days, toward the end of which it seemed not to be taking on any more color. After that, fears that it may have eventually started to putrefy drove me to take it out. The initial plan was to let it dry, rinse out any unfixed dye and bits of madder root, and put it back in the bath if the color wasn't satisfactory.
So, success? Well, for a given measure. The leather is certainly red. It's just not as rich or as even in color as we've come to expect. For all I know, this could just be what madder-red leather looked like in ancient times, but maybe there are factors that would result in a better color, such as larger vats or more frequent stirring.
One last note: The plastic bucket I used was also stained. I wonder, if I use it for future dyeing projects with other colors, will they pick up some pink from this one?