Mixing Times on Spiral Mixer

Hello,

I've been a professional artisan sourdough baker for over a decade. I've worked for an extended time at 8 bakeries and I've staged at other bakeries as well. 

Most bakeries seem to have mix times around 3-5 minutes on low speed, and then 4-8 minutes on high speed.  My current bakery mixes their staple sourdough for at least 15 minutes on low and at least 18 minutes on high. This feels very wrong to me, yet when I try to reduce their mix times, my bread no longer ferments on the same schedule. 

I'm trying to get to the bottom of this. They pretty much bulk all of their doughs for 3 hours before shaping, then we proof at room temp for an hour then in a retarder for about 4 hours before baking. 

I know their bread must be coming off the mixer hotter than mine. Honestly, I'm amazed their bread doesn't rip to shreds on the shaping table. 

Some of my staff is telling me our bread is flavorless, they argue it's because they are oxidizing the dough from the incredibly long mix times. 

I've only seen one other bakery use this extremely long mixing technique. Both bakeries that follow this technique are "European style" and I'm located in the states. 

Anyone else see mix times like this? Any thoughts about the whole process? I'm hypothesizing that my lower mix time dough will need 3-4 hours longer to bulk ferment to achieve the same gluten development as the 20 minute mix time dough. In this time, we might develop more flavor. This job has a high production volume and we don't have too much time to experiment, so I'm trying to improve my knowledge base before moving forward. 

Thanks y'all! Happy baking.