So it's important to keep your con high soon after being rotted so that it passes as many checks as possible. If you delay (especially as a low con race) and are already below max when you switch into your +con gear, you are probably toast.

To put it into context, I've had drow take full rots from Imperial High Priests (seem to recall it was 36 hours or something like that) and only be subject to a -4 con when the supp was in its final hour.