I would not do without windows. Because sometimes you want to change the air. We have 2 small windows on the gable sides - it is cheaper and less prone to later damage.
What do you mean by damages?
We would only use the attic as storage space. We will have a hip roof. Should it also be ventilated regularly?
I was not advised on that.
If the roof is not tightly insulated, there are no ventilation problems. However, it becomes very hot and very cold. Many things are not affected by this.
If done correctly, the roof is sealed on the inside so that warm air cannot escape through the roof and thus no condensation/moisture can form. However, when you open the attic hatch, air exchange between the living space and the attic inevitably takes place. In winter, the warm air rises and the relative humidity there increases. In any case, we have experienced that without ventilation you have much higher humidity and a "strangely" stuffy air there. This promotes corresponding mold growth or similar damage.