We had condensation boards on our '83 Ace but they're not fitted on our '01 Pageant, which has reduced fixed ventilation under EN1645 than older caravans - neither has suffered from this type of moisture.
All our "ventilation" is shut all day in winter although fixed ventilation is still working. We do make a point of using the Omnivent fan whenever the hob, oven or microwave are in use.
We also have no need to use dehumidifiers during storage, unlike some caravanners.
I can't explain why some suffer with moisture and others don't.