Although the performance may not be used to determine age, we might consider using the genre. Since the genre also produces ages which are not acceptable in traditional Indian world views, most Indians would use the tradition to define age. The ability to span different ethnic groups is another common benchmark. This is best illustrated by a simple model put forth by the anthropologist, Robert Redfield in the early to middle part of the 20th century. It is in this same manner that Carnatic classical music spans the diverse cultures of Tamil Nadu, Kerala, Carnatica, or Andhra Pradesh.
Cultural connotations are also a benchmark for determining whether something is classical.
This brings up the curious question of how many classical dance forms there are in India. Since all the various schools of dance are deficient in one or more of the benchmarks, one may argue that there are no classical dance forms in India. I think that most people would be dissatisfied with this proposition. I think that this too, is unacceptable to most people. Therefore we will try and steer a middle path.