As I always say, "Temperature control is the key to effective dough management". I'm betting that variations in finished dough temperature are creating greater differences in your dough than differences in kneading/mixing. A thermometer is cheap and it is easy to control finished dough temperature through minor adjustments in the temperature of the water that is added to make the dough. Depending upon how you are handling the dough after mixing, a difference of only a few degrees in finished dough temperature over 50+ hours can have a rather dramatic impact upon the finished dough at the time of use. If you are not already doing so, I would suggest getting a note book (baker's journal) to keep track of your experiments over time. This will allow you to get a better feel for your dough, and develop a history of what works and what doesn't work in your specific application. Be careful though, as you might end up like Norma, with the curiosity of a cat and never ending desire to improve upon your dough. Norma, please take that as the compliment that it's intended to be.
Tom Lehmann/The Dough Doctor