Nice one mate
The seeing is the important thing for bring out any detail in Saturn.
I'm no expert, but I don't see anything wrong with lots of frames, but flip the processing on its head and if you get say 10k frames, try stacking just the best 10-15% and see what happens. You should be able to see a difference. If not, then the seeing is magically consistent.
You should find that stacking so many frames is actually blurring the image, if the seeing is all over the place like it is whenever I try
so by recording so many more frames it gives you a larger selection of frames to choose from.
I'm sure there is a point of diminishing returns...but the more good frames you capture the better IMO. Just make sure your scope is cooled, etc, to maximise your chances.
Btw, field rotation doesn't matter as Registax will take care of that during stacking.