I stopped at level 5 as well. I already have a peacock from another event, and the prize for completing the building to level 10 is the fountain (which I didn't want). In answer to other posts, events aren't about buildings usually, unless you like the deco. Events are about the prizes. Leveled buildings help you earn the different prizes depending on the event. You just have to decide what level of participation you want to earn something that is deco only, or if the item has drops you need.