| Darkside Users dont spontaniously lose body parts, there is always a reason, as others pointed out, lost in battle or something. Only way I could see a Darksider having body parts just drop off is because they are a Leper and the strain the darkside puts on their body has made it even weaker. Not to say that physically they are weak, so much as The Dark Side has a much higher price then just being an evil twisted jerk off.
Sidious maybe old, and is probally old as hell, and is probally using the force to elongate his life span, but because of the darkside his looks like a withered old husk (that can throw massive bolts of force lightning and other nasty stuff like that) Jedi masters who are and have been just as old, while look old, still look like they are in pretty damn good condition. The darkside takes a toll on the body, but its not like it just picks up a meat cleaver and goes, "Well.... Today I think I'm gonna take that foot of yours." |