I tend to assume that IKEA furniture shouldn't be actually taken apart once put together, and so far that's worked out fine for us. There are some pieces that are obviously repeatable (table legs screwed into metal mounting brackets) but with a lot of the steps you can feel as you're doing it the first time that it's not going to work well if you have to undo it.
True. Adding a few 2" screws (into pilot holes) makes an enormous difference to the rigidity of their (e.g.) wardrobes and kitchen units. Even on first assembly, but especially if you have to take apart and rebuild.
IIRC when we wanted to move one of the pretty large IKEA dressers that had to be at least partially disassembled to fit through the door there was no non-destructive way to dismantle it. And that was not about trivial things like the back panel being nailed, but about fasteners of the actual structural parts being inaccessible once you put the whole thing together. One would think that going through the assembly steps in reverse should work, but for some reason it did not. I ended up breaking few structural braces (~18x48mm pieces of fiberboard) at the back of the thing to take it apart and replacing that with wooden beams of the same size.
