This is my opinion and is not intended to degrade anyone's efforts in modeling.
When I got back into modeling late last year, I was amazed at the methods that are now being used to finish models. Amazed yes, but also wondering with all the references out there for modelers to use in their projects, how can such efforts show realistic portrayals of actual aircraft. To some extent, you will see aircrafts with heavy weathering in the real world, but that is in conditions that prevent the maintenance of the exterior finish.
When a person modifies his or her project to reflect a planes upgrades with aftermarket kits, scratch building parts, cutting and pasting new parts to reflect the latest real life version, then finish the model with extreme weathering however beautiful that makes the model, it still tends to show it on the more artistic side.
My abilities are limited to say the least, but that's okay. I build to suit myself, and that goes to what everyone is writing about. TO EACH THEIR OWN. What makes one modeler happy with how they complete their project, doesn't sit well with another.
I won't use preshading myself, because it doesn't seem natural, and truth be known, it takes more time and effort to do for me. I enjoy looking at other people's work and say to myself, "If only I had a tenth of their talent to do that."
I believe moderation reflects the real aircraft as it is in any condition, well that is unless the plane has been regulated to the bone yard, then any and all extreme weathering is a okay. Years of neglect will do that to any object.
Extreme or in moderation, weathering reflects the individuals choice.