I usually break down all my MOCs after I take pictures of them and post the pictures online. Mainly because I don't want to loose the pics after having already destroyed the MOC. Because of my (somewhat) limited supply of castle/landscape pieces, I need to use them for my next build.
Although I do this, it is always half heartedly, as I wish I could display and show my MOCs to others. Its so nice to see a MOC in person than just a picture of it. Usually the only people who see my MOCs in person beside myself is my family.
On the other hand my pirate ship: http://www.flickr.com/photos/93632612@N ... 011482624/
will be two years old this coming July!
Because of the colour scheme and limited use of blue and yellow in the castle theme it will probably stay together forever.
I think building for the LCC makes me have to destroy and rebuild my MOCs so as to continue the storyline, and get multiple entries for contests like the GC6.