But, there are nights during which large scopes show no more detail than smaller instruments, and the effect isn't due to OTA thermal equilibration kinetics.
People say that, but it has never, ever been my experience. Even on poor nights the seeing usually settles down occasionally, and if you keep looking an 8-inch will, by the end of the evening have shown far more than a 3.5-inch.
Try living closer to the more turbulent section of the jet stream. The Winter of 2011-2012 was terrible here. There wasn't one clear night I schlepped out a 10" or 12" scope that paid off.
Don't misunderstand me though. On average, we used to have enough good nights that scopes with large objectives or mirrors were put to good use. I hope that particularly bad Winter was an anomaly.