Use 'decrepitude' to describe extreme old age, often implying poor condition or quality. The antique clock teetered on the edge of decrepitude.
Pro Tip 2/3
Physical Condition
'Decrepitude' often describes something worn out or weakened over time, not just old. After years of neglect, the bridge was a picture of decrepitude.
Pro Tip 3/3
Negative Feeling
The word conveys a negative, sometimes pitiful feeling about the subject's condition. Watching the decaying manor sink into decrepitude was a sorrowful sight.