Well, yes and no. Sometimes a combination of a part hot and part cold can be worse than all at maximum possible temperature (e.g. nitrogen purge connected to a very hot line or Pumps lines one operating one spare, or PSV lines one operating one spare). At least in terms of loads. Maybe here is not the case but as a designer you should first investigate all possible scenarios, then to retain only the worst.
Of course when PCV is operating, downstream is at operating temperature or close.
Best regards,
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Dan