What was the largest Lego set you've ever built and would you do it again?

My kid bought me a Back to the Future DeLorean for my birthday, about 2000 pieces.

Initially I thought it was kind of a mis-gift, something they would enjoy more than me since I hadn't built a set since they were small and needed my help, but I made it a point to crack it open instead of letting it sit and it turned out to be quite enjoyable.