Jerste,
Thanks for chiming in.
Many times desparate for a shot, I've shot across the inside of a warm vehicle---better half driving, me in the passenger seat---into cold outside air. Blurry pics almost every time. So heat cold thermals are real and just something we have to deal with when shooting long glass.
Another thing I'm sure is possible, I've yet to do MFA (micro focus adjust, a Sony term since I'm a Sony guy and can't remember Nikon's term) on the D500+500PF. I'll get around to it sometime this winter when I'm house bound.
Robert