All the stages come back at the end of the event. I recommend getting the mission awards on hard as that gives a decent amount of money and support items without as much energy usage or items if your team is too weak for z hard.
I got a solid line up with a few UR's. I'm rather well covered and have completed the entire storyline on all difficulties and any events that have so popped up. Not that some haven't been a good challenge here and there.