I would say rather than shorten it, they stagger it. Theres actually four differnt events, so why not change them every week? Theres toting, zombie apocalypse, banners and the trials. I would say start with banners, cause they are hard to get people for, then trials, then zombies and end with toting. Also limit how many zones have events at a time. Make it 1 zone per side at a time.