In all the talk of graphical downgrades no one seems much preoccupied with 'why?'. Why build something and then proceed to tear it down, piece by piece, in the hope that ever more diminished expectations about the final product won't be severe enough to...
Don't kill your Deadlings if you don't have to - they're pretty valuable.
Don't forget you can switch to different creatures on the fly. This is handy for switch pushing.
If there's an obstacle blocking your way, cut it out.