Its a timer when whatever structure is destroyed, and humans do have it too, in theory it was 'faster' to deconstruct a structure thats about to die if you plan on rebuilding it, however, with the deconstruct timer servers running R1CHs code have, it probably isn't the case. I guess it was also meant so that sawing/shooting/killing the old structures would have a sort of penalty timer to balance it a bit with the deconstruct timer.