Is that a lot? I ferment my regular wheat bread for over 24h. (Started some off this morning as it happens, will likely bake it tomorrow evening.)
Interesting you say that though, because I find three days about the limit, starts to really over-ferment, becoming really 'pockety', even at refrigeration temperatures. I suppose if I did it all in there as you imply, no fermentation time at room temp. at all, that might be better?
How active is your sourdough starter? Commercial yeast by contrast tends to be very active, so timings are shorter.
That said, I think they cultivate newer rye varieties to be less rich with enzymes. I presume that is to meet the requirements of industrial baking.