There are certain limits in the event. For example, once you've expanded your park to the maximum (7 expansions), you can't get any more points for it. There's also a certain limit to how many points you can earn when aliens duplicate (Space Park) and when you vanish a ghost with Light (Spooky Park). Namely, it's 1000 points.  Once you reach this limit, you will no longer receive points for these actions. 

Similarly, once you've maxed out an attraction, you can't get any more points from that attraction. You can stash it and build a new ride in its place to earn more rewards.