In 2005 we arrived on the last day. They actually do start dismantling things overnight. But it takes a while and you will still get to see several beautiful topiaries.
Here's something you might enjoy, since you're missing the big show. We stumbled onto it during that trip. One evening, park at Epcot and then take the monorail to MK for a late snack or parade or fireworks. Then, when you take the monorail back to Epcot to get your car, Epcot will be closed. But as the monorail rides around the park, you can see the workers dismantling the topiaries. There were a lot of trucks and workers scurrying around. I found it fascinating. (But I'm easily fascinated, I might add.)