No, actually the guiding got worse as the night wore on! By 4AM my subs were close to 3 arc seconds in my second system 10 feet away from the CEM120EC2
I think that what happened was that the mirror finally reached equilibrium and that the seeing improved between 7PM and 9PM. My imaging partner (who is vastly better at this than I am) never images at our location until about 2 hours after sunset. His advice to me when I was initially disappointed was to "wait" which proved to be correct. Once the temp stopped dropping I was surprised at the resultant change in image quality.
Nevertheless, I'm still thinking that there's something going on with the encoders, I'm just in a sweet spot of some kind. I'm very curious to see what happens when the big camera comes back.
I also use a 25" F8 RC scope from time to time. We actually use an air conditioner to cool that scope just before/after sunset or we get oblong stars sometimes all night. That scope is a truss design and we still needed fans to keep the airflow laminar where the truss ends and there is a short tube. It never occurred to me that the PW needed some extra cool down as it's been in New Mexico at 8000 feet for a long time where the thin air cools causes faster cooling and less tube current. (Or at least that's my latest crackpot theory.)