I think when you have them coming to prey distress, you can go straight from one sound to the next, and it works well. I'll go directly from fights to den raids, to pup distress, because that makes sense. When I howl, I wait. I'll run a series of howls, then pause for a few minutes. If they are taking a long time to come in, (call ins are 30mins or more), and I know I need to sit there for a while, I'll pause between each sound, but basically that's because it's hard to make noise for 45 minutes without running out of interesting sounds to play.