you are assuming the flight is IFR under ATC control
what about VFR outside CAS, perhaps not receiving no ATC service at all.
Then refer to the previous advice to avoid the area or call the appropriate flight service station or ATC unit about 5 to 10 minutes before you enter the area and ask if it is hot or cold. Make sure when you plan a flight through an advisory, restricted, or danger zone that you also plan enough fuel to divert around them without eating into your reserve fuel.
If my route takes me through that DA then I have unknowingly entered into an active danger area?
The first thing a regulator will say is "that sounds like a you problem." It is your responsibility to make sure you don't enter those areas and checking during pre-flight only means the area was not active then. Maintain situational awareness dictates by also checking in flight.
An example of just how quickly NOTAMs become active: I was once cleared by ATC through military airspace during a scheduled airline flight that was NOTAM'd inactive (cold) when the dispatcher sent the flight plan release. It was near to a 200 nm short-cut from the original flight planned route, so we were happy to accept as it would give my crew a chance to use a real washroom and eat lunch when we landed. ATC told us a third of the way through the area was now active (hot) and instructed us to make an immediate 90-degree turn and intercept the original route.
Treat NOTAMs as though they were a weather forecast and get updates on the ones that you think may change.