A WebmasterWorld thread rightly asks Why does it take 3 hours to see ads - pause ads? Normally, when one wants to pause an ad, they want it paused virtually immediately. Google works that way.
One member reports, "We paused several high traffic orders and 5 hours later there's still no slow down in our traffic."
The official response from Microsoft?
The average time to pause or resume a campaign is 3 hours, it's sometimes more, sometimes less. The product team is working to make this shorter, and once we get this resolved I'll let you know.
So they are working on it.
Forum discussion at WebmasterWorld.