There's nothing wrong with keeping them lubricated. I can't see that you'd need any more than water-based lubes such as WD40 on the hinges as long as it won't ingress into any electrical connectors.
I doubt you'd need anything thicker, just spray them up with your general maintenance of door hinges, bonnet hinges etc.
I would think that WD40 would boil off very quickly on an exhaust component - if there is an exposed slider or hinge then a high-temperature grease would probably be a better bet.
