Step 1: Recall the therapy list.
Panchakarma includes Vamana, Virechana, Basti and Nasya, each with its own contraindications by age and strength
Step 2: Recall the age-related caution.
Virechana, the purgation therapy, is considered too taxing for a very elderly patient because of the fluid and strength loss it causes
Step 3: Conclude the answer.
This makes Virechana the therapy generally avoided beyond 70 years of age
\[ \boxed{Virechana} \]