Did we see Yoda's body suffer massive deterioration from massive force feats, no we did not. There is a reason for this, while Palpatine was still able to augment himself to move incredibly quickly in Episode III, that didn't change the fact his body suffered some serious damage; damage that Yoda did not suffer.
While the darkside may be quicker and easier, it also seems to carry a terrible price for the wielder from a physical standpoint.
Shouldn't a detoriating body be a plus for a dark-sider? Especially with ones like Sion or Sidious who have been known to channel pain into rage.