I was tempted to swap out Addy body around 12 (when the AC component of it became more or less useless), but kept it, and I feel the extra 2 points of DR have been useful. If you have a Bladesmark Docent and are willing to commit the docent slot to it until 20, then you have more flexibility to dump Addy Body while levelling, IMO.
Wax mentioned that above I believe, and this is what I would do if I had that docent while levelling my FvS.
Note, the BM Docent has a slightly less useful type of DR (/magic) than Addy Body / WF (Admantium), so it's not as much protection in all cases as Addy Body + WF DR enhances.