When does vacuum advance kick in?

I wouldn't necessarily call it "kick in". That makes it sound dramatic. It ain't. lol Most any part throttle operation, you have vacuum advance. Such as cruising down the road at a set speed......or perhaps light acceleration. That's of course if it's connected to ported vacuum, which is usually best. Connected to full manifold vacuum, it's "kicked in" pretty much all the time, except for hard acceleration, when vacuum drops out anyway.