Do event modifiers like flash crash or others have a duration?
Events are instantaneous. They may have effects that persist for a long time afterwards, but they are not themselves ongoing. Thats what situations (red and green circles) are for.
What I meant was say you get the labeling of video games event and you choose to put warning labels on them. This gives you a (I forget exactly) a +10% with parents and a -10% with youth. How long do these effects last? Will you always have a -10% malus with youth voters?
Generally speaking no, these effects will slowly degrade over time, dependent on the specific event. I do plan eventually to make that clearer in the graphs for the righ-click popup on those effects.