Do you mean in terms of experience where rather than age, the term Elder is more of a rank of power? Or do you mean when they become advanced in age where they are an actual Elder?
Because we can look at it two ways. Orcs are a race of people whoās culture circle around the wisdom of their Ancestors. The Ancestors, while in their afterlife, have gained insight on things that are valuable to the orcs still living. Future sight, predictions, wisdom of the past. Orcs who are advanced in age may gain respect for what they know, the amount of experience they have gained. Drekāthar, even in his advanced age, was very powerful. He went through a lot and also learned a lot. So he was a both a person of power and respect in age.
Now the only āElder shamanā I actually see named/remember (so far) is Drekāthar, Mother Kashur, Nerāzhul and Magatha and a Wolvar named Elder Moky from WotLK. Each of these characters, even Moky, all are in a position of the highest rank they could be. Three of these are leaders/Chieftains with Moky and Mother Kashur being the highest ranking shaman in their group. An elder shaman existing next to a chieftain in an orcish clan have almost the same level of respect and power as a chieftain. They are extremely respected and their huts are about as important looking as the chieftainās would be.
Mother Kashur, who was the teacher for Drekāthar, was also something I feel we donāt know much about which was she was the āClan Motherā. Greatmother Geyah became the Clan Mother after Mother Kashur passed away, and she is the Mother figure for all of Garadar, where as Kashur was the Mother for all of the Frostwolf Clan. She is also considered an Elder.
The term Elder and Mother seem to be titles of leadership and rank for shaman who have reached a position of respect akin to a Chieftain or are a Chieftain. Especially seeing there is an NPC named Mother Omāra , who appears (?) to have been a past Shadowmoon Chieftain. She is a part of the quest to tame Gaara.
So Elder Shaman as a rank is someone who is about as powerful as a Chieftain. The age does not seem to be too much of a factor. Only because the Elder Shaman of clans tend to be the that rank for many many years until they pass away, and then are replaced by their student.
However maybe a shaman who is just up there in age maybe a shaman elder.
Regardless, the term āelderā is a term of respect among the orcish people. They lean in the direction of being a native culture, so respect for those who have gained wisdom and experience will be important to them. Respecting ones elders among the orcs is probably a bit more meaningful than just holding open the door for them.
I hoped this help, it was fun to do a bit of research to make sure I had the answers right!