I’ve always wondered about this...I largely take it for granted that my filters are parfocal, but a lot depends on the filter wheel and how they’re fixed in, etc.
At f/4, I re-run the autofocus routine as the scope is suitably twitchy (narrow CFZ) and it takes less than a minute to run, but wonder about the slower f/ratios...I wonder how much it is visible
Needless to say, the faster the scope, the more sensitive it will be to temperature dependent focus shift.