The WTS does suggest that older elders remain elders but not have duties to handle. Elder emeritus?
"Not too long ago, however, an adjustment was made. Older elders were asked to hand over some of their weightier responsibilities to younger elders. In what way?
The new arrangement is that circuit overseers and field instructors discontinue those particular types of service when they reach 70 years of age. Also, elders who are 80 years old will turn over to younger elders various other assignments, such as being coordinator of a Branch Committee or being coordinator of the body of elders in a local congregation. How have these dear older elders responded to this adjustment? They have shown loyalty to Jehovah and to his organization!
“I was totally in agreement with the decision,” comments Ken, who served as coordinator of a Branch Committee for almost 49 years. “In fact, on the very morning I found out, I had prayed to Jehovah, expressing the need for a younger brother to serve as the coordinator.” Ken’s reaction is typical of the sentiments expressed by faithful older ones worldwide. Of course, since they loved serving their brothers, there was some initial disappointment." September 2018 "Older Christians" p. 8-9