Number of resonating structures (hypothetical) To my knowledge, resonance happens where more than one lewis stucture can represent the compound with no shift in sigma bonds

so, suppose in a simple conjugated system even like 1-3 pentadiene , two forms are well known, i want to know if a third form where each atom has completely filled or completely empty p orbitals should also be taken into consideration, as technically, there is nothing wrong with it, I accept that it's "contribution" will be negligible, but it should be counted in all POSSIBLE resonating structures

https://commons.wikimedia.org/wiki/File:Naphthalene_resonance_structure.svg 

similar argument here, a lot more can be created if we allow charge separation of pi bond

EDIT: The question is whether there is a convention of some sort which tells us which ones to count which ones not (if we cant tell the magnitude of difference in stability of the structure)
Resonances structures are a model of the quantum mechanical orbital mixing.  To my mind they are a complete farce.  They are also quite useful

A model is a simplification of a problem, usually based on ignoring negligible factors.  So this question really distills down to what is negligible and what isn't? 

That depends on roughly two factors:


The conditions of reaction.  


Are the conditions strongly ionic or acidic?  Then charge separation may become relevant.


The rigor of the problem. 


Is this for a high school course? A Ph.D. thesis? A bar-room chat with your mates?

Unfortunately, like most of chemistry, there is not an absolute answer here.